text:
(also RFC 393)
Updates RFC 137Network Working Group T. O'Sullivan Request for Comments: 139 Raytheon NIC: 6717 7 May 1971 Discussion of TELNET Protocol The attached discussion is an extension of RFC 137, NIC #6717, and is presented to provide useful background to designers and implementers to help them interpret the proposed Protocol and evaluate it in preparation for further discussion at the Atlantic City meetings. While the views in the discussion represent those of various TELNET committee members, they should not be interpreted as being the agreed view of committee. They are the author's understanding of some of the arguments and background to the PROTOCOL proposed in the TELNET PROTOCOL recommendations. * See Footnotes to attached discussion for changes to RFC 137. Discussion of TELNET PROTOCOL The use of a standard, network-wide, intermediate representation of terminal code between sites eliminates the need for using and serving sites to keep information about the characteristics of each other's terminals and terminal handling conventions, but only if the user, the using site, and the serving site assume certain responsibilities. 1. The serving site must specify how the intermediate code will be mapped by it into the terminal codes that are expected at that site. 2. The user must be familiar with that mapping. 3. The using site must provide some means for the user to enter all of the intermediate codes, and as a convenience, special control signals, as well as specify for the user how the signals from the serving site will be presented at the user terminal. Other schemes were considered but rejected. For example, a proposal that the using site be responsible to transmit to and from the code expected by the serving site was rejected since it required that the using site keep tables of all serving site codes and provide mapping for each case. The information would require constant maintenance as new hosts were added to the network. O'Sullivan [Page 1]
RFC 139 Discussion of TELNET Protocol 7 May 1971 Since it is not known how the current or future sites will specify the mapping between the network-wide standard code (7 bit ASCII in an 8 bit field) and the codes expected from their own terminals, it seems necessary to permit the user to cause every one of the 128 ASCII codes, plus (for full user power) selected control signals (either of a TELNET control nature, or of a special terminal nature such as break or attention). There was strong feeling about the importance of the user/system interface at the using site, but equally strong feeling that this problem is one of local implementation and should reflect the using site installation philosophy rather than the subject to network-wide standards. Some topics of consideration in this area are: 1. How to represent special graphics, not available at the using site, at the user's terminal. 2. Treatment of upper/lower case problem on TTY 33 and 35. a. Representing lower-case output. b. Providing users with shift and shift lock signals. 3. Incorporating editing capability in TELNET. 4. Extending user options in Network mode not available to local users, e.g., hold output kill print 5. Permit users to specify how keyboard input is to be translated, e.g., let a character from the terminal cause a specified string to be sent by the user's TELNET. In early discussions, there was pressure to get a simple statement of protocol out early to permit early use of selected systems. The counter pressure to provide a richer set of protocol in the first release was also present. Work started in the direction of the latter, but the complexities introduced were not necessary for early use of the network. The proposed solution to the TELNET protocol problem seems to provide a mechanism for a minimum implementation (to be discussed later) while providing a basis for developing richer sets of protocol for present and future use in terminal applications, process-process communications, and use by other conventions to pass data or control information. O'Sullivan [Page 2]
RFC 139 Discussion of TELNET Protocol 7 May 1971 The understanding that ASCII be used as a network-wide code has been established for some time. Its use in TELNET provided a problem with respect to the limitation of a maximum character set of 128. Some systems provide for more than this number in their operation, and therefor, as serving sites cannot map on a one for one basis. Each such serving site could probably provide a reasonably useful character set, including all system control signals, by mapping 128 of its codes and just not provide a network user access to the other codes. However, any character left out might later be used in a major application at that site as a special control signal. This could result in denying network users the facility offered by that application. Serving sites are, therefor, encouraged to provide a full mapping between the ASCII code and the code used on the serving system. The ASCII code for ESC (known to some as ALT MODE) has been selected as an escape [1]. For each serving site character not mapped on a one for one basis, the serving site can specify an escape character or string of escape characters (preferably a printable graphic) to represent it. Thus, the user could enter the full set of serving site code from any network terminal operating through the Network Virtual Terminal (NVT) ASCII convention. The serving site, in generating output directed at the user's terminal, would be expected to map out such a character and transmit the appropriate ESC character or string of ESC characters. Example: A serving site, whose normal code is EBCDIC, has specified that cent ([5]) has not been mapped on a one for one basis and that to transmit the character, users must enter ESC followed by C. At a using site, the TELNET implementers have decided to try to print out all ESC characters using \ to indicate ESC. On receipt of the representation for cent, the user would see \C on his print-out. The representation of the end of a physical line at a terminal is implemented differently on network HOSTS. For example, some use a return (or new line) key, the terminal hardware both returns the carriage or printer to start of line and feeds the paper to the next line. In other implementations, the user hits carriage return and the hardware returns carriage while the software returns to the terminal a line feed. The network-wide representation will be carriage return followed by line feed. It represents the physical formatting that is being attempted, and is to be interpreted and appropriately translated by both using site and serving site. O'Sullivan [Page 3]
RFC 139 Discussion of TELNET Protocol 7 May 1971 Example: A Multics user is working, through the network, on some serving site HOST. In the course of the session, the user has numerous occasions to hit New Line on his Mod 37 TTY. Each time the Multics system is awakened by a New Line interrupt, the line of buffered characters is passed to TELNET where it is scanned for special characters. If none is found, carriage return followed by line feed is inserted where New Line was entered, and the line is turned over to the NCP for transmission. When the TELNET finds the carriage return line feed sequence in the data stream coming from the serving site, the two characters are replaced with New Line code and sent to the terminal. The decision to have the assumed condition for echo be that the using site will provide any echo necessary for its terminals was taken because of the difficulties faced by some installations that cannot turn off their echo or that have terminals that print locally as a result of key strokes. Serving sites could take the position "let the user turn my echo off", but this seems an unnecessary burden on the user. In addition, some serving sites may choose not to supply any echo service, in which case the no echo assumption will supply a network-wide condition, while other assumptions would give a mixed starting connection. [2] The convention of using "I ECHO", "YOU ECHO" seems to fill both the requirements for dynamic echo control and for a minimum implementation of TELNET Protocol. [3] An agreed-upon exchange to pass echo control (i.e., two sites exchange the I ECHO/YOU ECHO codes) results in passing the control from one site to the other. Example: A serving site is exchanging control information with the USER in an area where the serving system asks for pass word and wants to suppress the printing of the pass word at the using site's user terminal. (In this case, the using site has the ability to control the print capability at the user's terminal.) Using site has been echoing to the user's terminal. Serving Site to Using Site (--->) I ECHO Using Site to Serving Site (<---) YOU ECHO --->Pass word: <--- (User enters password at terminal) O'Sullivan [Page 4]
RFC 139 Discussion of TELNET Protocol 7 May 1971 ---> (No echo sent) ---> YOU ECHO <--- I ECHO After the exchange, the original normal condition is re- established. If the using site did not have dynamic echo control installed in its TELNET implementation, the serving site would have signaled I ECHO several times, received no response, and assumed that the using site could not comply proceeding to call for the pass word without the normal protection of inhibiting print. TELNET control signals are of two types: one that results in transmission of signals down the network to a receiving site; the other intended for the user/process site only. The latter type will be discussed later. So far, we have discussed the former type, specifically dealing with echo control. The use of ESC should not be considered a TELNET-wide standard, but a convention limited to the 7 bit ASCII mode of transmission. Other conventions, to be incorporated later, may include binary transmission, EBCDIC, etc. Presumably, each will have its own convention for an escape character to extend its code set. Since it is expected that conventions other than ASCII will be implemented under TELNET, a code to indicate a DATA TYPE representing each set of conventions will be employed. The control code X'AO' has been selected to represent the ASCII convention in TELNET. Since a number of applications may wish to transmit transparently (i.e., 8 bit binary data), X'Al' is being reserved for that purpose. The TELNET control code X'A2' is reserved for an expected set of EBCDIC conventions. The DATA TYPE is expected as the first byte of data over a TELNET connection. Minimum implementations will be aided by providing a default. That is, if the first byte over a connection has the high order bit set as zero, then the transmission has begun in ASCII mode. Each set of conventions, i.e., each DATA TYPE will be expected to have a convention for that DATA TYPE to signal that it is returning to control mode. This return may be for the purpose of making use of an existing control codes or to change data type. X'88' is used [4]. Example: At the using site, a terminal has a special device on it (e.g., plotter, laboratory instrument, control box, etc.) that is controlled by binary code in 8 bit bytes. The terminal uses a special "enter" code that routes signals to the device and cuts O'Sullivan [Page 5]
RFC 139 Discussion of TELNET Protocol 7 May 1971 off printing at the terminal until a special "leave" signal is received from the driving process. The driving process in this case is at a remote serving site. It is assumed in this example that a DLE convention is used for transparent transmission, a single DLE signal representing return to control. Normal transmission has been in ASCII. Driving Process (at Serving Site) to Using Site) ----> X'88'X'A1' Using Site to Serving Site <---- X'88'X'88' -----------> ENTER code...8 bit binary bytes... Using Site TELNET to Terminal | | V Enter code...8 bit binary bytes... Terminal Turn printer off, feed transparently to special device, look for LEAVE signal ------------> 8 bit binary bytes...LEAVE signal...single DLE X'A0' <----------- X'88'X'88 ------------> Message | | V 8 bit binary data...LEAVE signal MESSAGE O'Sullivan [Page 6]
RFC 139 Discussion of TELNET Protocol 7 May 1971 _Terminal_ During this sequence of exchanges - at the terminal, feed binary data to special device until LEAVE signal is sensed, strip off LEAVE signal, turn on printer and block data path to special device, print MESSAGE at terminal. There is a special control signal on some terminals that has no corresponding bit pattern in ASCII, but is transmitted by a special electrical signal. This control signal is ATTN on a 2741 and BREAK on a teletype. The ASCII DATA TYPE in TELNET will use the code X'81' to represent BREAK. (There is a corresponding control signal for use from serving sites to using sites for reverse break, and it is assigned the code X'82'). Some systems treat the break as an extra code available for use in conjunction with the data stream. For example, one system uses break as a special editing code meaning "delete the current line to this point". In these cases, the code may simply be inserted in the data stream with no special additional action by the user. Other systems use BREAK or ATTN in a special interrupt fashion, to mean stop processing the application and give me the supervisor, or cancel the present job, etc. (Other systems use normal characters for this purpose, such as "Control C".) In these cases, because of differences in the ways both serving and using sites operate, it is necessary to take a route in addition to the normal TELNET data stream to signal that the special control signal is imbedded in the data stream. _Examples-Problem_ The PDP-10 normally will, when it fills its input buffer, continue to accept characters from a terminal examining each to see if it is a control character, then act on it if it is or throw it away if it is not. Since the TELNET server at the serving site is at the mercy of the NCP with respect to controlling the bunching, and therefor, arrival at the TELNET of bursts of characters, TELNET implementations might be expected to choke off flow to the buffers until they are ready to accept characters without throwing them away. Under this condition, the serving process might be outputting to the using terminal, the input buffers fill up, and a control C get stuck in the data stream that has been choked off. O'Sullivan [Page 7]
RFC 139 Discussion of TELNET Protocol 7 May 1971 A similar problem could occur with the Multics or some IBM system as a server. The user at a using site gets into an output loop at the serving site and wants to break the process without having to release his TELNET connection. The buffers clog the connection, transmission is choked off, and the control C break, or other user control signal gets stuck in the pipeline. _Example - Solution_ The user at the using site knows he is entering a special control signal (break, ATTN, control C, etc.) and follows it with an X'80'. (The local instructions at using sites for accomplishing this may differ from site to site.) Using Site TELNET to Serving Site Insert X'80' in Data Stream Using Site TELNET to Using Site NCP Send an INS Sending Site NCP to TELNET Server Look out, here she come Serving Site TELNET Does its special thing until it sees X'80' then resumes normal handling Thus, depending on the server's local implementation to provide adequate service, a special handling of the data stream can be invoked whenever an INS is received in order to get the special character. When it sees X'80', it recognizes it as a SYNC character and knowing that the special character has been passed on, strips the X'80' from the data stream and returns to normal mode. If the X'80' arrives before the INS, a counting scheme can keep the activity appropriate to the serving site conditions. This approach to handling selected special characters or signals relieves the using TELNET processes from having to recognize the special serving site characters, as well as from having to know how the serving site wants to handle them. At the same time, the O'Sullivan [Page 8]
RFC 139 Discussion of TELNET Protocol 7 May 1971 procedure requires only a minimum level of user understanding of the serving site. This seems appropriate, since the TELNET ASCII conventions are providing a Network Virtual Terminal, not a Network Virtual User. The ability of the user to cause the using site TELNET to send any combination of ASCII characters in a string, and only that combination, is viewed as important to the user utility of the TELNET ASCII conventions. Because of this, some user sites may find it necessary to provide special local TELNET control signalling from the user to the using site. _Examples_ A user on a line at a time system (Multics, System 360, GECOS, etc.) is working through the Network on a serving site that operates a character at a time. The application is a debugging aid that permits the user to type in a memory location = to which it will respond with n where n represents the current contents of that location. The serving site process does not expect to see the location = followed by a carriage return line feed sequence. The user at the using site should be able to type in the location, follow it with a signal to suppress the end of a line convention, followed by a new line or return, and expect the location number = to be transmitted immediately without an end of line sequence. In another case, a using site has decided that it is convenient to accumulate four characters at a time and transmit them to the serving site, unless an end of line is observed, in which case the end of line sequence is sent preceded by whatever number of characters have been accumulated, (presumably three or less). In the same debugging application, the address is such that the end does not correspond with the four character buffer demarcation. The user should have the ability to enter a code for "transmit immediately" in place of the Carriage Return in order to preserve neat formatting, and expect the address to be sent to the serving site. TELNET controls have been discussed and those introduced to date are probably sufficient for an early implementation of TELNET ASCII convention. There will be a need to establish a mechanism for the controlled assignment (on request by Network Sites), and announcement of DATA TYPE and CONTROL codes. It should be noted that some controls are network-wide TELNET controls, while others are specific to the ASCII Data Type. It should be further recognized that some local control messages do not require a corresponding network-wide code. O'Sullivan [Page 9]
RFC 139 Discussion of TELNET Protocol 7 May 1971 While it is recognized that even a minimum implementation of TELNET for a using site is expected to permit the user to send any selected ASCII string (and only that string) to the serving site, it is not necessary for a serving site to implement a full mapping from ASCII to local code, nor is it necessary for either the using or serving sites to implement all control codes. _Example - Using Site_ A minimum implementation of the TELNET protocol for the using site would permit ignoring (and stripping) any control signals from the serving site since they would all either require agreement or acknowledgement (e.g., DATA TYPE, ECHO CONTROL, etc.) or can be ignored with no particularly harmful results (e.g., reverse break). _Example - Serving Site_ A minimum implementation of the TELNET protocol for the serving site could provide one for one mapping for the most important 128 serving system controls and graphic signals, and ignore all control signals. It would be helpful if a minimally implemented receiving site, when it recognizes an incoming control signal for which appropriate reaction is not available, could respond with X'87' (The following not implemented at this site) and follow it with the code just received. Whenever an ASCII TELNET connection is lost, it should be assumed that the process at the other end of the connection has been quit, aborted, failed, etc. In this way, a minimum using site installation can fail to implement the break and break synchronization, and have the user rely on the using site local procedure for leaving a running local process and returning to the supervisor to break a connection to a remote serving site. _Example_ User recognizes that he is caught in an output loop and wishes to stop his user process at the serving site. The serving site requires a break, but the using site minimum implementation has not made it available. Even if it had, the INS was not implemented and could not be used to unblock the input pipe. Locally, the using site convention for leaving a process and getting to supervisory level is to hit the attention key on the 2741 terminal. The user does this and is passed to the supervisor where he signals to release the TELNET connection. The serving O'Sullivan [Page 10]
RFC 139 Discussion of TELNET Protocol 7 May 1971 site, seeing that an ASCII TELNET connection has been lost, assumes that the user is ended either normally or abnormally. Serving site cancels the user's process. The user tries again by re-establishing the connection, logging in again, re-initiating the process, etc. Other conventions under TELNET may make quite different assumptions about lost connections, and some may go as far as dynamic establishing and releasing of connections. The proposed TELNET ASCII implementation leaves much uncovered, but seems to permit early simple implementation with varying levels of capability, along with the capacity to expand in several ways to meet others needs. There is an important open question. Should a PROTOCOL such as TELNET provide the basis for extending a system to perform functions that go beyond the normal capacity of the local system. For example, a local system may not provide functions such as Hold Output, Kill Print, etc., but it could extend it for network purposes through TELNET. If so, to what extent should such extensions be thought of as Network-wide standards as opposed to purely local implementations. Endnotes [1] Please drop the (s) at the end of "character" in paragraph 3, page 3, RFC 137, NIC #6714. [2] Also make note that the starting assumption in the initial exchange between using site and serving site will be that the using site will (if necessary) provide echo and the serving site will not. [3] Note: Please change RFC #137, NIC #6714, page 4 - Code X'85' to read Reserved. [4] Please note on page 4 of RFC 137 that the receipt of an X'88' should be responded with by the receiver sending a double signal, i.e., X'88'X'88' if the new DATA TYPE can be handled. [5] Cent sign [This RFC was put into machine readable form for entry] [into the online RFC archives by Lorrie Shiota, 1/02] O'Sullivan [Page 11]


text:
There's A New Buyer In Town: Millennials
The U.S. homeownership rate rose in 2017 for the first time in 13 years. Millennial home ownership was the largest increase of any age group from 2016-2017. This rapid increase could be due to multiple factors. Rent prices are at an all-time high, wages are rising at 2.9% per year (the fastest since 2009), and are in fact the largest population in U.S. history.*
In the next five years, a whopping 66% of millennials are expected to buy homes…and will most likely buy yours.
*statistics sourced from:
https://www.nar.realtor/research-and-statistics/research-reports/home-buyer-and-seller-generational-trends | https://www.wsj.com/articles/homeownership-rate-rises-in-2017-for-first-time-since-2004-1517334537 | http://www.goldmansachs.com/our-thinking/pages/millennials/ | http://www.pewresearch.org/fact-tank/2018/05/04/more-than-a-million-millennials-are-becoming-moms-each-year/ | https://www.housingwire.com/articles/42748-millennials-lead-all-other-generations-in-buying-homes

subset: commoncrawl


text:
New Car/Review
Toyota Camry XLE (2002)
SEE ALSO: Toyota Buyer's Guide
by Brendan Hagin and Mikele Schappell-Hagin
SPECIFICATIONS Manufacturer's Suggested Retail Price $ 25,405 Price As Tested $ 31,139 Engine Type DOHC 24-valve 3.0 Liter V6 w/SMFI* Engine Size 183 cid/2995 cc Horsepower 192 @ 5300 RPM Torque (lb-ft) 209 @ 4400 RPM Wheelbase/Width/Length 107.1"/70.7"/189.2" Transmission Four-speed automatic Curb Weight 3359 pounds Fuel Capacity 18.5 gallons Tires (F/R) 215/60R16 all-season Brakes (F/R) Disc (ABS)/disc (ABS) Drive Train Front-engine/front-wheel-drive Vehicle Type Five-passenger/four-door Domestic Content N/A Coefficient of Drag (Cd.) N/A PERFORMANCE EPA Economy, miles per gallon city/highway/average 20/28/25 0-60 MPH 8.5 seconds 1/4 (E.T.) 16.5 @ 86.5 mph Top-speed 120 mph * Sequential multi-point fuel injection
BRENDAN - The Toyota Camry is another one of those cars that we've never been assigned to check out, Mikele, so I was looking forward to getting behind the wheel of one for a week. It's been the best-selling car in the country for the past four years and at around 400,000 units sold last year, it outsold it closest competitor by nearly 20,000 vehicles. My dad wrote-up the first Camry back in '83 and even then it was hard for him to find anything that wasn't "right.". He called it the perfect small car for a small family. But at 3300 pounds, I don't think the '02 XLE version of the Camry can be called "small" anymore. The platform of last year's model had been basically unchanged during the previous 10 years but this new model is longer, wider and taller than before and according to the press kit, it has considerably more interior room than the last version. The XLE is the luxury model of the lineup and our V6-powered tester had almost all the bells-and-whistles in the Toyota repertoire. It's a leather upholstered boulevard cruiser that comes very close to being a luxury car.
MIKELE - You know what a "bug" I am about safety, Bren, so I really appreciated the safety items on our XLE. It had a skid control system that automatically applies individual braking power on any wheel if the car gets out of line, a traction control device that reduces wheel spin during acceleration and a brake assisting program that takes over if the driver doesn't apply enough pedal pressure to fully take advantage of the anti-lock braking system. It has side airbags that drop down to help protect passengers in the back seats as well as the front in the event of a side impact. The front airbags operate on a couple of different modes. If a frontal impact is relatively mild, the bags inflate at a lesser rate, but if the impact is more harsh, they inflate faster.
BRENDAN - There's two other versions of the '02 Camry, the XL model which is as close as you can come to an "entry-level," and the SE which is a return to the concept of a "sporting" Camry. The SE suspension is tighter and the steering is pumped up a bit to give its driver more road "feel" at highway speed. To differentiate the SE from the other Camrys, it was given a different grille, fog lights and a couple of other cosmetic differences. To make sure its stiffer suspension updates can be utilized to their fullest, Toyota even added some bolt-on modifications such as an auxiliary front strut tower support. The 192-horse V6 that was in our fancy XLE model is a holdover and does the same quiet job it's done in the past, but Toyota seems to be particularly proud of the 2.4-liter four-banger that's also available in the Camry. It's all new and puts out 157 horsepower and 162 pound/feet of torque. It can be had in all three of the Camrys and it's the only one that can be ordered with a five-speed stick shift. Toyota marketers estimate that the four-cylinder with the four-speed automatic is going to account for two-thirds of all the Camry sales in '02. There's so many engine, transmission and trim combinations that buyers can tailor-make a Camry to suit their individual need and tastes.
MIKELE - And they all have a long list of standard features that include air conditioning and all the rest of the usual "extras." The option package that came on our test XLE included leather upholstery, powered front seats, a hot-shot sound system and a moon roof. It's kind of a pricey package at $4300, but this is no "stripper" rental car. But at $1100, optional safety items like skid control and computer-assisted braking are bargains.
BRENDAN - Not being much on esthetics, I can only comment that the lines of the new Camry are more "swoopy" than the old one and that there's a remarkable family resemblance between the new Camry and the Echo, Pruis and the rest of the passenger cars in the lineup.
MIKELE - Brendan, I'm really proud of you. Usually the only thing you notice about the cars we test is that the driver's seat is cramped for you, how "cool" the sound system is and what color paint is on the outside.


text:
From Adirondack Day Hikes: Pine Orchard by Barbara McMartin reprinted in Adirondack Sports and Fitness, June 2000.
"Pine Orchard Trail begins on private land in James Flater's front yard leads to a knoll with an unusual history. A very old road that traversed the knoll dates back to the early nineteenth century. Parts of the forest along the road were logged a long time ago and, in fact, there are parts that today appear as if they never had been logged. For a strange reason Pine Orchard was spared. Nature had destroyed the forest on the knoll with a tremendous windstorm. These winds came from the hurricane of 1815 and they leveled the knoll. Pines reestablish best when the soil has been disturbed and thus many pines sprouted on the knoll. They were of course too small to attract early lumbermen. Then nature dealt a second blow. Sometime, when the trees here were fairly small, a blight hit. The trees kept growing, but because the tops of many were gone, the trees branched, making two or three trunks in a clump. Now, lumbermen don't want pines that do not have tall, straight, single trunks. So they never cut these trees. They probably would not have logged them anyway, because sometime early in the nineteenth century this land became Forest Preserve, meaning that no trees could ever be cut there again. So, this short walk will lead you to a stand of the largest pines you will find in the southern Adirondacks. One tree is so large that three people, arms outstretched, cannot reach around it. Other trees are filling in among the old pines. On the southern slopes you will find spruce trees of enormous size for spruce (they never get much above 30 inches in diameter). On the knoll's northern slopes you will find magnificent hemlocks. Also interspersed among the pines are large maples that came along after the pines were big enough to shade them when they were young.
To find the trail, drive to Wells on NY 30 and just before the road turns to cross the Sacandaga River, head straight ahead on Griffen Road. Follow that road for 0.7 mile and turn right on Windfall Road and follow it for just over a mile to a fork. Take the right fork and follow it for two miles. The dirt road narrows and climbs until you see a sign at the side of the road "visitors parking."
Mr. Flater, retired Colonie police chief, and his family have put that there for walkers. Park and continue on the road, following it across his front lawn until you reach state land. Just beyond the state land boundary, a snowmobile trail comes in on your right and the marked trail continues generally northeast. The first 0.8 mile of trail is generally downhill through young forest to a bridge, then the trail winds through more mature forest to a second stream crossing in another 0.6 mile. After the trail makes a sharp bend to the northwest, it begins to climb the knoll. You will find the tallest pines near the top of the knoll.
The walk to cover the knoll and return is less than five miles, quite easy, and should take under three hours. You won't find much better stand of forest in the Adirondacks that is so accessible."
WinterCampers.com made this our camping destination on Jan 26-27 as Matt, Mark, Len Sparky and I dragged in the tipi for a pleasant overnight in the woods. Given the easy trail description Matt and Jim experimented with sleds. The Otter II sled proved just as easy to pull and with it's deeper tray was less likely to get snagged on branches and overturn than the Paris Company Expedition Sled.
It was an easy hike in, below Matt confers with Len, Mark and Sparky.
Once we were among the large white pines we set up camp. These trees are 300 year old giants that centuries ago would have warranted protection by the English Crown for the sole use of the mast makers of the Royal Navy; straight-grained white pines six feet in diameter and perhaps two hundred feet tall. Mark got cozy with a white pine on the hike in.
We arrived at our campsite shortly after noon and had our lunches. While most of us packed our own lunch at least one newly wed had theirs packaged and labeled.
While Len prepared a fire site, Mark & I cut wood and Sparky and Matt set up the tipi.
After much coaxing and the sacrificing of the small dry tipi wood, Firemaster Len finally got a decent blaze and we sat around the fire until 9pm.
There was a little snow during the night which periodically slid down the tipi leaving slightly banked sides in the morning.
We packed up, marched out and had a great breakfast at the diner in Wells.


text:
Sewing Machines
Machine Accessories
Polyneon No.40 1000m Spools. Madeiras 100% polyester embroidery thread. Polyneon is constructed of a specially developed raw material which eliminates looping, puckering and virtually all thread breaks. Suitable for almost any application, Polyneons unique formula makes this thread extremely durable and smooth running. Vibrant colours are glossy, as well as resistant to chlorine bleach, making Polyneon the ideal thread for embroidering on uniforms, safety garments and commercial linens.
There are no reviews yet.
Be the first to review "1963 Polyneon 40 – 1000m" Cancel reply


text:
Tenerife Royale is a leading independent Tenerife real estate agency based on the border of Los Cristianos and Las Americas on the sunny South coast of Tenerife. We are full and active members of A.I.P.P. (the watchdog for the industry) and our approach centres around a Professional Quality Service to our customers enabling us to advise on all aspects of buying and selling land, residential and commercial property in Tenerife. We have been established for over 20 years helping buyers and sellers alike.
Tenerife Royale - Tenerife Estate agents offering advice on the purchase of land and property for sale in Tenerife for both residential and holiday home purposes.
We are not 'tied' to any particular Tenerife property developer or property chain. We are totally independent established Tenerife estate agents which means that we can offer impartial advice and opinions on all Tenerife property matters. We are fully regulated by A.I.P.P. (the watchdog for the industry) in order to help and protect you the consumer.
Personal Service
Your dealings with this Tenerife estate agent will be with a senior member of staff (director) who will ensure that you receive the correct information and advice and assist with all your Tenerife property enquiries in a friendly, business like manner. We will not try and 'sell' you anything. We will, however, provide unbiased guidance and direct you to the most suitable Tenerife properties and ensure that you receive the proper legal advice. Our primary aim is to provide you with the best possible service, which in turn means that you, will recommend us to your friends and associates. If you are interested in buying property in Tenerife, please register your requirements with us.
Tenerife is the perfect location for owning property. Whether you are seeking an active lifestyle found in the resort areas or a gentle relaxed lifestyle found in Tenerife's sleepy villages, the variety and choice of property in Tenerife is excellent from affordable Tenerife apartments to ultra luxury penthouses and villas. Couple this with the excellent climate of Tenerife with its almost 52 weeks of sunshine a year and you have the perfect combination of a holiday home lifestyle and perhaps an additional income from letting your Tenerife property to the many visitors that come to the island all year round.
Tenerife offers more than just the bustling tourist areas. From the highest peak in Spain (Mount Teide 12,000 feet) with its dramatic volcanic and lunar style landscapes to the lush sub tropical forests, sandy beaches, elegant cities and quiet villages, Tenerife offers a myriad of contrasts with vast areas of outstanding natural scenery.
Tenerife the largest of the Canary Islands, although under the sovereignty of Spain, has its own autonomous Government and special status within the E.E.C. which means that your investment in property in Tenerife is protected by European law.


text:
In this collection of Blog posts, there is a very large selection of blogs and articles written all about the world of Linear Actuators. Here you will find everything you could ever need to know about Actuators, from how they are built, to the many different types of linear actuators, to how to install, run and operate them. There are also many articles about how they are used and installed in many every day applications with plenty of videos, tutorials, wiring diagrams and much more.
Linear Actuators are used in just about every application and industry you can think of, plus there are many different types of Actuators each with its own set of unique features and characteristics that make each one suitable for that specific function. Electric linear Actuators are what FIRGELLI® has focused on for over 20 years so this set of articles should cover just about every topic you can think of when it comes to the world of Linear Motion and Electric point to point motion control.


text:
Crochet Pattern: Goldfish Applique
By Rachel Choi – 23 CommentsNeed goldfish? Here is a tiny little fishy to sew onto any item that you can think of. Use it to decorate clothing or bags. Or use it as a cute fridgie (refrigerator magnet) or pin. You can even embroider a face if you desire. Have fun crocheting a school of little goldfish! |
Skill Level: |
Finished Size: 2″ (5 cm) long, 1″ (2.5 cm) tall
Note: to adjust the size of the goldfish, use a larger or small hook and different weight of yarn
Materials: Medium Weight Yarn (small amount) Crochet Hook H (5.00 mm) |
Crochet Pattern: Goldfish
Round 1: ch 7, sc in second ch from hook, hdc in next ch, dc in next 2 ch, hdc in next ch, sc in last ch, working into opposite side of chain into remaining loops, sc in next ch, hdc in next ch, dc in next 2 ch, hdc in next ch, sc in last ch, sl st in first sc made joining to beginning of round
Round 2: ch 3, turn, 2 dc in next st, finish off.
Using photo as a guide, embroider face to goldfish.
If you need help crocheting this goldfish applique, let me know and I'll be glad to help!


text:
open, openat, creat - open and possibly create a file
Standard C library (libc
, -lc
#include <fcntl.h>
int open(const char *pathname, int flags, ...
/* mode_t mode */ );
int creat(const char *pathname, mode_t mode);
int openat(int dirfd, const char *pathname, int flags, ...
/* mode_t mode */ );
/* Documented separately, in
int openat2(int dirfd, const char *pathname,
const struct open_how *how, size_t size);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
Since glibc 2.10:
Before glibc 2.10:
The open() system call opens the file specified by
. If the specified file does not exist, it may
optionally (if O_CREAT is specified in flags
be created by open().
The return value of open() is a file descriptor, a small, nonnegative integer that is an index to an entry in the process's table of open file descriptors. The file descriptor is used in subsequent system calls ( read(2), write(2), lseek(2), fcntl(2), etc.) to refer to the open file. The file descriptor returned by a successful call will be the lowest-numbered file descriptor not currently open for the process.
By default, the new file descriptor is set to remain open across an execve(2) (i.e., the FD_CLOEXEC file descriptor flag described in fcntl(2) is initially disabled); the O_CLOEXEC flag, described below, can be used to change this default. The file offset is set to the beginning of the file (see lseek(2)).
A call to open() creates a new open file
description, an entry in the system-wide table of open files. The
open file description records the file offset and the file status flags
(see below). A file descriptor is a reference to an open file
description; this reference is unaffected if pathname
subsequently removed or modified to refer to a different file. For
further details on open file descriptions, see NOTES.
The argument flags
must include one of the following
access modes
O_WRONLY, or O_RDWR. These request
opening the file read-only, write-only, or read/write, respectively.
In addition, zero or more file creation flags and file status flags
can be bitwise ORed in flags
. The file creation flags
are O_CLOEXEC, O_CREAT,
O_TMPFILE, and O_TRUNC. The file
status flags are all of the remaining flags listed below. The
distinction between these two groups of flags is that the file creation
flags affect the semantics of the open operation itself, while the file
status flags affect the semantics of subsequent I/O operations. The file
status flags can be retrieved and (in some cases) modified; see
fcntl(2) for details.
The full list of file creation flags and file status flags is as follows:
The file is opened in append mode. Before each write(2), the file offset is positioned at the end of the file, as if with lseek(2). The modification of the file offset and the write operation are performed as a single atomic step.
O_APPEND may lead to corrupted files on NFS filesystems if more than one process appends data to a file at once. This is because NFS does not support appending to a file, so the client kernel has to simulate it, which can't be done without a race condition.
Enable signal-driven I/O: generate a signal (SIGIO by default, but this can be changed via fcntl(2)) when input or output becomes possible on this file descriptor. This feature is available only for terminals, pseudoterminals, sockets, and (since Linux 2.6) pipes and FIFOs. See fcntl(2) for further details. See also BUGS, below.
Enable the close-on-exec flag for the new file descriptor. Specifying this flag permits a program to avoid additional fcntl(2) F_SETFD operations to set the FD_CLOEXEC flag.
Note that the use of this flag is essential in some multithreaded programs, because using a separate fcntl(2) F_SETFD operation to set the FD_CLOEXEC flag does not suffice to avoid race conditions where one thread opens a file descriptor and attempts to set its close-on-exec flag using fcntl(2) at the same time as another thread does a fork(2) plus execve(2). Depending on the order of execution, the race may lead to the file descriptor returned by open() being unintentionally leaked to the program executed by the child process created by fork(2). (This kind of race is in principle possible for any system call that creates a file descriptor whose close-on-exec flag should be set, and various other Linux system calls provide an equivalent of the O_CLOEXEC flag to deal with this problem.)
If pathname
does not exist, create it as a regular file.
The owner (user ID) of the new file is set to the effective user ID of the process.
The group ownership (group ID) of the new file is set either to the
effective group ID of the process (System V semantics) or to the group
ID of the parent directory (BSD semantics). On Linux, the behavior
depends on whether the set-group-ID mode bit is set on the parent
directory: if that bit is set, then BSD semantics apply; otherwise,
System V semantics apply. For some filesystems, the behavior also
depends on the bsdgroups
and sysvgroups
mount options
described in mount(8).
The mode
argument specifies the file mode bits to be applied
when a new file is created. If neither O_CREAT nor
O_TMPFILE is specified in flags
, then
is ignored (and can thus be specified as 0, or simply
omitted). The mode
argument must be supplied
if O_CREAT or O_TMPFILE is specified
in flags
; if it is not supplied, some arbitrary bytes from the
stack will be applied as the file mode.
The effective mode is modified by the process's umask
in the
usual way: in the absence of a default ACL, the mode of the created file
is (mode & ~umask)
Note that mode
applies only to future accesses of the newly
created file; the open() call that creates a read-only
file may well return a read/write file descriptor.
The following symbolic constants are provided for mode
00700 user (file owner) has read, write, and execute permission
00400 user has read permission
00200 user has write permission
00100 user has execute permission
00070 group has read, write, and execute permission
00040 group has read permission
00020 group has write permission
00010 group has execute permission
00007 others have read, write, and execute permission
00004 others have read permission
00002 others have write permission
00001 others have execute permission
According to POSIX, the effect when other bits are set in
is unspecified. On Linux, the following bits are also
honored in mode
Try to minimize cache effects of the I/O to and from this file. In general this will degrade performance, but it is useful in special situations, such as when applications do their own caching. File I/O is done directly to/from user-space buffers. The O_DIRECT flag on its own makes an effort to transfer data synchronously, but does not give the guarantees of the O_SYNC flag that data and necessary metadata are transferred. To guarantee synchronous I/O, O_SYNC must be used in addition to O_DIRECT. See NOTES below for further discussion.
A semantically similar (but deprecated) interface for block devices is described in raw(8).
If pathname
is not a directory, cause the open to fail. This
flag was added in Linux 2.1.126, to avoid denial-of-service problems if
opendir(3) is called on a FIFO or tape device.
Write operations on the file will complete according to the
requirements of synchronized I/O data
integrity completion.
By the time write(2) (and similar) return, the
output data has been transferred to the underlying hardware, along with
any file metadata that would be required to retrieve that data (i.e., as
though each write(2) was followed by a call to
fdatasync(2)). See NOTES below
Ensure that this call creates the file: if this flag is specified in
conjunction with O_CREAT, and pathname
exists, then open() fails with the error
When these two flags are specified, symbolic links are not followed:
if pathname
is a symbolic link, then open()
fails regardless of where the symbolic link points.
In general, the behavior of O_EXCL is undefined if
it is used without O_CREAT. There is one exception: on
Linux 2.6 and later, O_EXCL can be used without
O_CREAT if pathname
refers to a block device.
If the block device is in use by the system (e.g., mounted),
open() fails with the error EBUSY.
On NFS, O_EXCL is supported only when using NFSv3 or later on kernel 2.6 or later. In NFS environments where O_EXCL support is not provided, programs that rely on it for performing locking tasks will contain a race condition. Portable programs that want to perform atomic file locking using a lockfile, and need to avoid reliance on NFS support for O_EXCL, can create a unique file on the same filesystem (e.g., incorporating hostname and PID), and use link(2) to make a link to the lockfile. If link(2) returns 0, the lock is successful. Otherwise, use stat(2) on the unique file to check if its link count has increased to 2, in which case the lock is also successful.
(LFS) Allow files whose sizes cannot be represented in an
(but can be represented in an off64_t
) to be
opened. The _LARGEFILE64_SOURCE macro must be defined
(before including any
header files) in order to obtain this
definition. Setting the _FILE_OFFSET_BITS feature test
macro to 64 (rather than using O_LARGEFILE) is the
preferred method of accessing large files on 32-bit systems (see
Do not update the file last access time (st_atime
in the
inode) when the file is read(2).
This flag can be employed only if one of the following conditions is true:
The effective UID of the process matches the owner UID of the file.
The calling process has the CAP_FOWNER capability in its user namespace and the owner UID of the file has a mapping in the namespace.
This flag is intended for use by indexing or backup programs, where its use can significantly reduce the amount of disk activity. This flag may not be effective on all filesystems. One example is NFS, where the server maintains the access time.
If pathname
refers to a terminal device—see
tty(4)—it will not become the process's controlling
terminal even if the process does not have one.
If the trailing component (i.e., basename) of pathname
is a
symbolic link, then the open fails, with the error
ELOOP. Symbolic links in earlier components of the
pathname will still be followed. (Note that the ELOOP
error that can occur in this case is indistinguishable from the case
where an open fails because there are too many symbolic links found
while resolving components in the prefix part of the pathname.)
This flag is a FreeBSD extension, which was added in Linux 2.1.126, and has subsequently been standardized in POSIX.1-2008.
See also O_PATH below.
When possible, the file is opened in nonblocking mode. Neither the open() nor any subsequent I/O operations on the file descriptor which is returned will cause the calling process to wait.
Note that the setting of this flag has no effect on the operation of
poll(2), select(2),
epoll(7), and similar, since those interfaces merely
inform the caller about whether a file descriptor is "ready", meaning
that an I/O operation performed on the file descriptor with the
O_NONBLOCK flag clear
would not block.
Note that this flag has no effect for regular files and block devices; that is, I/O operations will (briefly) block when device activity is required, regardless of whether O_NONBLOCK is set. Since O_NONBLOCK semantics might eventually be implemented, applications should not depend upon blocking behavior when specifying this flag for regular files and block devices.
For the handling of FIFOs (named pipes), see also fifo(7). For a discussion of the effect of O_NONBLOCK in conjunction with mandatory file locks and with file leases, see fcntl(2).
Obtain a file descriptor that can be used for two purposes: to indicate a location in the filesystem tree and to perform operations that act purely at the file descriptor level. The file itself is not opened, and other file operations (e.g., read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), mmap(2)) fail with the error EBADF.
The following operations can
be performed on the resulting
file descriptor:
fchdir(2), if the file descriptor refers to a directory (since Linux 3.5).
fstat(2) (since Linux 3.6).
fstatfs(2) (since Linux 3.12).
Duplicating the file descriptor (dup(2), fcntl(2) F_DUPFD, etc.).
Getting and setting file descriptor flags (fcntl(2) F_GETFD and F_SETFD).
Retrieving open file status flags using the fcntl(2) F_GETFL operation: the returned flags will include the bit O_PATH.
Passing the file descriptor as the dirfd
argument of
openat() and the other "*at()" system calls. This
includes linkat(2) with AT_EMPTY_PATH
(or via procfs using AT_SYMLINK_FOLLOW) even if the
file is not a directory.
Passing the file descriptor to another process via a UNIX domain socket (see SCM_RIGHTS in unix(7)).
When O_PATH is specified in flags
, flag
bits other than O_CLOEXEC,
O_DIRECTORY, and O_NOFOLLOW are
Opening a file or directory with the O_PATH flag requires no permissions on the object itself (but does require execute permission on the directories in the path prefix). Depending on the subsequent operation, a check for suitable file permissions may be performed (e.g., fchdir(2) requires execute permission on the directory referred to by its file descriptor argument). By contrast, obtaining a reference to a filesystem object by opening it with the O_RDONLY flag requires that the caller have read permission on the object, even when the subsequent operation (e.g., fchdir(2), fstat(2)) does not require read permission on the object.
If pathname
is a symbolic link and the
O_NOFOLLOW flag is also specified, then the call
returns a file descriptor referring to the symbolic link. This file
descriptor can be used as the dirfd
argument in calls to
fchownat(2), fstatat(2),
linkat(2), and readlinkat(2) with an
empty pathname to have the calls operate on the symbolic link.
If pathname
refers to an automount point that has not yet
been triggered, so no other filesystem is mounted on it, then the call
returns a file descriptor referring to the automount directory without
triggering a mount. fstatfs(2) can then be used to
determine if it is, in fact, an untriggered automount point
(.f_type == AUTOFS_SUPER_MAGIC).
One use of O_PATH for regular files is to provide the equivalent of POSIX.1's O_EXEC functionality. This permits us to open a file for which we have execute permission but not read permission, and then execute that file, with steps something like the following:
char buf[PATH_MAX];
fd = open("some_prog", O_PATH);
snprintf(buf, PATH_MAX, "/proc/self/fd/%d", fd);
execl(buf, "some_prog", (char *) NULL);
An O_PATH file descriptor can also be passed as the argument of fexecve(3).
Write operations on the file will complete according to the
requirements of synchronized I/O file
integrity completion (by
contrast with the synchronized I/O data
integrity completion
provided by O_DSYNC.)
By the time write(2) (or similar) returns, the output data and associated file metadata have been transferred to the underlying hardware (i.e., as though each write(2) was followed by a call to fsync(2)). See NOTES below.
Create an unnamed temporary regular file. The pathname
argument specifies a directory; an unnamed inode will be created in that
directory's filesystem. Anything written to the resulting file will be
lost when the last file descriptor is closed, unless the file is given a
O_TMPFILE must be specified with one of O_RDWR or O_WRONLY and, optionally, O_EXCL. If O_EXCL is not specified, then linkat(2) can be used to link the temporary file into the filesystem, making it permanent, using code like the following:
char path[PATH_MAX];
fd = open("/path/to/dir", O_TMPFILE | O_RDWR,
/* File I/O on 'fd'... */
linkat(fd, "", AT_FDCWD, "/path/for/file", AT_EMPTY_PATH);
/* If the caller doesn't have the CAP_DAC_READ_SEARCH
capability (needed to use AT_EMPTY_PATH with linkat(2)),
and there is a proc(5) filesystem mounted, then the
linkat(2) call above can be replaced with:
snprintf(path, PATH_MAX, "/proc/self/fd/%d", fd);
linkat(AT_FDCWD, path, AT_FDCWD, "/path/for/file",
In this case, the open() mode
determines the file permission mode, as with
Specifying O_EXCL in conjunction with O_TMPFILE prevents a temporary file from being linked into the filesystem in the above manner. (Note that the meaning of O_EXCL in this case is different from the meaning of O_EXCL otherwise.)
There are two main use cases for O_TMPFILE:
Improved tmpfile(3) functionality: race-free creation of temporary files that (1) are automatically deleted when closed; (2) can never be reached via any pathname; (3) are not subject to symlink attacks; and (4) do not require the caller to devise unique names.
Creating a file that is initially invisible, which is then populated with data and adjusted to have appropriate filesystem attributes (fchown(2), fchmod(2), fsetxattr(2), etc.) before being atomically linked into the filesystem in a fully formed state (using linkat(2) as described above).
O_TMPFILE requires support by the underlying filesystem; only a subset of Linux filesystems provide that support. In the initial implementation, support was provided in the ext2, ext3, ext4, UDF, Minix, and tmpfs filesystems. Support for other filesystems has subsequently been added as follows: XFS (Linux 3.15); Btrfs (Linux 3.16); F2FS (Linux 3.16); and ubifs (Linux 4.9)
If the file already exists and is a regular file and the access mode allows writing (i.e., is O_RDWR or O_WRONLY) it will be truncated to length 0. If the file is a FIFO or terminal device file, the O_TRUNC flag is ignored. Otherwise, the effect of O_TRUNC is unspecified.
A call to creat() is equivalent to calling
open() with flags
equal to
The openat() system call operates in exactly the same way as open(), except for the differences described here.
The dirfd
argument is used in conjunction with the
argument as follows:
If the pathname given in pathname
is absolute, then
is ignored.
If the pathname given in pathname
is relative and
is the special value AT_FDCWD, then
is interpreted relative to the current working
directory of the calling process (like
If the pathname given in pathname
is relative, then it
is interpreted relative to the directory referred to by the file
descriptor dirfd
(rather than relative to the current working
directory of the calling process, as is done by open()
for a relative pathname). In this case, dirfd
must be a
directory that was opened for reading (O_RDONLY) or
using the O_PATH flag.
If the pathname given in pathname
is relative, and
is not a valid file descriptor, an error
(EBADF) results. (Specifying an invalid file descriptor
number in dirfd
can be used as a means to ensure that
is absolute.)
The openat2(2) system call is an extension of openat(), and provides a superset of the features of openat(). It is documented separately, in openat2(2).
open(), openat(), and creat() can fail with the following errors:
The requested access to the file is not allowed, or search permission
is denied for one of the directories in the path prefix of
, or the file did not exist yet and write access to the
parent directory is not allowed. (See also
Where O_CREAT is specified, the
or protected_regular
sysctl is
enabled, the file already exists and is a FIFO or regular file, the
owner of the file is neither the current user nor the owner of the
containing directory, and the containing directory is both world- or
group-writable and sticky. For details, see the descriptions of
in proc(5).
(openat()) pathname
is relative but
is neither AT_FDCWD nor a valid file
O_EXCL was specified in flags
refers to a block device that is in use by the system
(e.g., it is mounted).
Where O_CREAT is specified, the file does not exist, and the user's quota of disk blocks or inodes on the filesystem has been exhausted.
already exists and O_CREAT and
O_EXCL were used.
points outside your accessible address space.
See EOVERFLOW.
While blocked waiting to complete an open of a slow device (e.g., a FIFO; see fifo(7)), the call was interrupted by a signal handler; see signal(7).
The filesystem does not support the O_DIRECT flag. See NOTES for more information.
Invalid value in flags
O_TMPFILE was specified in flags
, but
neither O_WRONLY nor O_RDWR was
O_CREAT was specified in flags
and the
final component ("basename") of the new file's pathname
invalid (e.g., it contains characters not permitted by the underlying
The final component ("basename") of pathname
is invalid
(e.g., it contains characters not permitted by the underlying
refers to a directory and the access requested
involved writing (that is, O_WRONLY or
O_RDWR is set).
refers to an existing directory,
O_TMPFILE and one of O_WRONLY or
O_RDWR were specified in flags
, but this
kernel version does not provide the O_TMPFILE
Too many symbolic links were encountered in resolving
was a symbolic link, and flags
O_NOFOLLOW but not O_PATH.
The per-process limit on the number of open file descriptors has been reached (see the description of RLIMIT_NOFILE in getrlimit(2)).
was too long.
The system-wide limit on the total number of open files has been reached.
refers to a device special file and no
corresponding device exists. (This is a Linux kernel bug; in this
situation ENXIO must be returned.)
O_CREAT is not set and the named file does not exist.
A directory component in pathname
does not exist or is a
dangling symbolic link.
refers to a nonexistent directory,
O_TMPFILE and one of O_WRONLY or
O_RDWR were specified in flags
, but this
kernel version does not provide the O_TMPFILE
The named file is a FIFO, but memory for the FIFO buffer can't be allocated because the per-user hard limit on memory allocation for pipes has been reached and the caller is not privileged; see pipe(7).
Insufficient kernel memory was available.
was to be created but the device containing
has no room for the new file.
A component used as a directory in pathname
is not, in fact,
a directory, or O_DIRECTORY was specified and
was not a directory.
(openat()) pathname
is a relative pathname
and dirfd
is a file descriptor referring to a file other than a
O_NONBLOCK | O_WRONLY is set, the named file is a FIFO, and no process has the FIFO open for reading.
The file is a device special file and no corresponding device exists.
The file is a UNIX domain socket.
The filesystem containing pathname
does not support
refers to a regular file that is too large to be
opened. The usual scenario here is that an application compiled on a
32-bit platform without -D_FILE_OFFSET_BITS=64
tried to open a
file whose size exceeds (1<<31)-1
bytes; see also
O_LARGEFILE above. This is the error specified by
POSIX.1; before Linux 2.6.24, Linux gave the error
EFBIG for this case.
The O_NOATIME flag was specified, but the effective user ID of the caller did not match the owner of the file and the caller was not privileged.
The operation was prevented by a file seal; see fcntl(2).
refers to a file on a read-only filesystem and
write access was requested.
refers to an executable image which is currently
being executed and write access was requested.
refers to a file that is currently in use as a swap
file, and the O_TRUNC flag was specified.
refers to a file that is currently being read by
the kernel (e.g., for module/firmware loading), and write access was
The O_NONBLOCK flag was specified, and an incompatible lease was held on the file (see fcntl(2)).
The (undefined) effect of O_RDONLY | O_TRUNC varies among implementations. On many systems the file is actually truncated.
The POSIX.1-2008 "synchronized I/O" option specifies different variants of synchronized I/O, and specifies the open() flags O_SYNC, O_DSYNC, and O_RSYNC for controlling the behavior. Regardless of whether an implementation supports this option, it must at least support the use of O_SYNC for regular files.
Linux implements O_SYNC and
O_DSYNC, but not O_RSYNC. Somewhat
incorrectly, glibc defines O_RSYNC to have the same
value as O_SYNC. (O_RSYNC is defined
in the Linux header file <asm/fcntl.h>
on HP PA-RISC, but
it is not used.)
O_SYNC provides synchronized I/O file
integrity completion, meaning write operations will flush data and all
associated metadata to the underlying hardware. O_DSYNC
provides synchronized I/O data
integrity completion, meaning
write operations will flush data to the underlying hardware, but will
only flush metadata updates that are required to allow a subsequent read
operation to complete successfully. Data integrity completion can reduce
the number of disk operations that are required for applications that
don't need the guarantees of file integrity completion.
To understand the difference between the two types of completion,
consider two pieces of file metadata: the file last modification
timestamp (st_mtime
) and the file length. All write operations
will update the last file modification timestamp, but only writes that
add data to the end of the file will change the file length. The last
modification timestamp is not needed to ensure that a read completes
successfully, but the file length is. Thus, O_DSYNC
would only guarantee to flush updates to the file length metadata
(whereas O_SYNC would also always flush the last
modification timestamp metadata).
Before Linux 2.6.33, Linux implemented only the
O_SYNC flag for open(). However, when
that flag was specified, most filesystems actually provided the
equivalent of synchronized I/O data
integrity completion (i.e.,
O_SYNC was actually implemented as the equivalent of
Since Linux 2.6.33, proper O_SYNC support is provided. However, to ensure backward binary compatibility, O_DSYNC was defined with the same value as the historical O_SYNC, and O_SYNC was defined as a new (two-bit) flag value that includes the O_DSYNC flag value. This ensures that applications compiled against new headers get at least O_DSYNC semantics before Linux 2.6.33.
Since glibc 2.26, the glibc wrapper function for open() employs the openat() system call, rather than the kernel's open() system call. For certain architectures, this is also true before glibc 2.26.
openat2(2) Linux.
The O_DIRECT, O_NOATIME, O_PATH, and O_TMPFILE flags are Linux-specific. One must define _GNU_SOURCE to obtain their definitions.
The O_CLOEXEC, O_DIRECTORY, and O_NOFOLLOW flags are not specified in POSIX.1-2001, but are specified in POSIX.1-2008. Since glibc 2.12, one can obtain their definitions by defining either _POSIX_C_SOURCE with a value greater than or equal to 200809L or _XOPEN_SOURCE with a value greater than or equal to 700. In glibc 2.11 and earlier, one obtains the definitions by defining _GNU_SOURCE.
Under Linux, the O_NONBLOCK flag is sometimes used in cases where one wants to open but does not necessarily have the intention to read or write. For example, this may be used to open a device in order to get a file descriptor for use with ioctl(2).
Note that open() can open device special files, but creat() cannot create them; use mknod(2) instead.
If the file is newly created, its st_atime
, st_mtime
fields (respectively, time of last
access, time of last status change, and time of last modification; see
stat(2)) are set to the current time, and so are the
and st_mtime
fields of the parent directory.
Otherwise, if the file is modified because of the
O_TRUNC flag, its st_ctime
fields are set to the current time.
The files in the /proc/
directory show the
open file descriptors of the process with the PID pid
. The
files in the /proc/
directory show even more
information about these file descriptors. See proc(5)
for further details of both of these directories.
The Linux header file <asm/fcntl.h> doesn't define O_ASYNC; the (BSD-derived) FASYNC synonym is defined instead.
The term open file description is the one used by POSIX to refer to
the entries in the system-wide table of open files. In other contexts,
this object is variously also called an "open file object", a "file
handle", an "open file table entry", or—in kernel-developer parlance—a
struct file
When a file descriptor is duplicated (using dup(2) or similar), the duplicate refers to the same open file description as the original file descriptor, and the two file descriptors consequently share the file offset and file status flags. Such sharing can also occur between processes: a child process created via fork(2) inherits duplicates of its parent's file descriptors, and those duplicates refer to the same open file descriptions.
Each open() of a file creates a new open file description; thus, there may be multiple open file descriptions corresponding to a file inode.
On Linux, one can use the kcmp(2) KCMP_FILE operation to test whether two file descriptors (in the same process or in two different processes) refer to the same open file description.
There are many infelicities in the protocol underlying NFS, affecting amongst others O_SYNC and O_NDELAY.
On NFS filesystems with UID mapping enabled, open() may return a file descriptor but, for example, read(2) requests are denied with EACCES. This is because the client performs open() by checking the permissions, but UID mapping is performed by the server upon read and write requests.
Opening the read or write end of a FIFO blocks until the other end is also opened (by another process or thread). See fifo(7) for further details.
Unlike the other values that can be specified in flags
, the
access mode
values O_RDONLY,
O_WRONLY, and O_RDWR do not specify
individual bits. Rather, they define the low order two bits of
, and are defined respectively as 0, 1, and 2. In other
words, the combination O_RDONLY | O_WRONLY is a logical
error, and certainly does not have the same meaning as
Linux reserves the special, nonstandard access mode 3 (binary 11) in
to mean: check for read and write permission on the file
and return a file descriptor that can't be used for reading or writing.
This nonstandard access mode is used by some Linux drivers to return a
file descriptor that is to be used only for device-specific
ioctl(2) operations.
openat() and the other system calls and library functions that take a directory file descriptor argument (i.e., execveat(2), faccessat(2), fanotify_mark(2), fchmodat(2), fchownat(2), fspick(2), fstatat(2), futimesat(2), linkat(2), mkdirat(2), mknodat(2), mount_setattr(2), move_mount(2), name_to_handle_at(2), open_tree(2), openat2(2), readlinkat(2), renameat(2), renameat2(2), statx(2), symlinkat(2), unlinkat(2), utimensat(2), mkfifoat(3), and scandirat(3)) address two problems with the older interfaces that preceded them. Here, the explanation is in terms of the openat() call, but the rationale is analogous for the other interfaces.
First, openat() allows an application to avoid race
conditions that could occur when using open() to open
files in directories other than the current working directory. These
race conditions result from the fact that some component of the
directory prefix given to open() could be changed in
parallel with the call to open(). Suppose, for example,
that we wish to create the file dir1/dir2/xxx.dep
if the file
exists. The problem is that between the existence
check and the file-creation step, dir1
or dir2
might be symbolic links) could be modified to point to a different
location. Such races can be avoided by opening a file descriptor for the
target directory, and then specifying that file descriptor as the
argument of (say) fstatat(2) and
openat(). The use of the dirfd
file descriptor
also has other benefits:
the file descriptor is a stable reference to the directory, even if the directory is renamed; and
the open file descriptor prevents the underlying filesystem from being dismounted, just as when a process has a current working directory on a filesystem.
Second, openat() allows the implementation of a
per-thread "current working directory", via file descriptor(s)
maintained by the application. (This functionality can also be obtained
by tricks based on the use of /proc/self/fd/
dirfd, but less
The dirfd
argument for these APIs can be obtained by using
open() or openat() to open a directory
(with either the O_RDONLY or the
O_PATH flag). Alternatively, such a file descriptor can
be obtained by applying dirfd(3) to a directory stream
created using opendir(3).
When these APIs are given a dirfd
argument of
AT_FDCWD or the specified pathname is absolute, then
they handle their pathname argument in the same way as the corresponding
conventional APIs. However, in this case, several of the APIs have a
argument that provides access to functionality that is
not available with the corresponding conventional APIs.
The O_DIRECT flag may impose alignment restrictions on the length and address of user-space buffers and the file offset of I/Os. In Linux alignment restrictions vary by filesystem and kernel version and might be absent entirely. The handling of misaligned O_DIRECT I/Os also varies; they can either fail with EINVAL or fall back to buffered I/O.
Since Linux 6.1, O_DIRECT support and alignment restrictions for a file can be queried using statx(2), using the STATX_DIOALIGN flag. Support for STATX_DIOALIGN varies by filesystem; see statx(2).
Some filesystems provide their own interfaces for querying O_DIRECT alignment restrictions, for example the XFS_IOC_DIOINFO operation in xfsctl(3). STATX_DIOALIGN should be used instead when it is available.
If none of the above is available, then direct I/O support and alignment restrictions can only be assumed from known characteristics of the filesystem, the individual file, the underlying storage device(s), and the kernel version. In Linux 2.4, most filesystems based on block devices require that the file offset and the length and memory address of all I/O segments be multiples of the filesystem block size (typically 4096 bytes). In Linux 2.6.0, this was relaxed to the logical block size of the block device (typically 512 bytes). A block device's logical block size can be determined using the ioctl(2) BLKSSZGET operation or from the shell using the command:
blockdev --getss
O_DIRECT I/Os should never be run concurrently with the fork(2) system call, if the memory buffer is a private mapping (i.e., any mapping created with the mmap(2) MAP_PRIVATE flag; this includes memory allocated on the heap and statically allocated buffers). Any such I/Os, whether submitted via an asynchronous I/O interface or from another thread in the process, should be completed before fork(2) is called. Failure to do so can result in data corruption and undefined behavior in parent and child processes. This restriction does not apply when the memory buffer for the O_DIRECT I/Os was created using shmat(2) or mmap(2) with the MAP_SHARED flag. Nor does this restriction apply when the memory buffer has been advised as MADV_DONTFORK with madvise(2), ensuring that it will not be available to the child after fork(2).
The O_DIRECT flag was introduced in SGI IRIX, where it has alignment restrictions similar to those of Linux 2.4. IRIX has also a fcntl(2) call to query appropriate alignments, and sizes. FreeBSD 4.x introduced a flag of the same name, but without alignment restrictions.
O_DIRECT support was added in Linux 2.4.10. Older Linux kernels simply ignore this flag. Some filesystems may not implement the flag, in which case open() fails with the error EINVAL if it is used.
Applications should avoid mixing O_DIRECT and normal I/O to the same file, and especially to overlapping byte regions in the same file. Even when the filesystem correctly handles the coherency issues in this situation, overall I/O throughput is likely to be slower than using either mode alone. Likewise, applications should avoid mixing mmap(2) of files with direct I/O to the same files.
The behavior of O_DIRECT with NFS will differ from local filesystems. Older kernels, or kernels configured in certain ways, may not support this combination. The NFS protocol does not support passing the flag to the server, so O_DIRECT I/O will bypass the page cache only on the client; the server may still cache the I/O. The client asks the server to make the I/O synchronous to preserve the synchronous semantics of O_DIRECT. Some servers will perform poorly under these circumstances, especially if the I/O size is small. Some servers may also be configured to lie to clients about the I/O having reached stable storage; this will avoid the performance penalty at some risk to data integrity in the event of server power failure. The Linux NFS client places no alignment restrictions on O_DIRECT I/O.
In summary, O_DIRECT is a potentially powerful tool that should be used with caution. It is recommended that applications treat use of O_DIRECT as a performance option which is disabled by default.
Currently, it is not possible to enable signal-driven I/O by specifying O_ASYNC when calling open(); use fcntl(2) to enable this flag.
One must check for two different error codes, EISDIR and ENOENT, when trying to determine whether the kernel supports O_TMPFILE functionality.
When both O_CREAT and O_DIRECTORY
are specified in flags
and the file specified by
does not exist, open() will create a
regular file (i.e., O_DIRECTORY is ignored).