POSIX is an acronym for "Portable Operating System Interface", a family of standards specified by the IEEE for maintaining compatibility between operating systems.

learn more… | top users | synonyms

4
votes
1answer
1k views

Consequences of setting up POSIX locales

Small background of the situation: We are using several UBUNTU servers having English as working language; however having en_US locale set in machines we encounter problems with apt-cacher-ng ...
5
votes
1answer
163 views

Is there a command line tool to manage unix signals?

Is there a command runner like env, nice, nohup, etc., that can run a program with modified signals? In my case, I need something to reset SIGINT to SIG_DFL. Why do I need this? Because ...
0
votes
0answers
179 views

Getting CRC mismatch warnings in gdb on cygwin

When I run any program under gdb in cygwin shell I get following warnings... warning: the debug information found in "/usr/lib/debug//usr/bin/cyggcc_s-seh-1.dll.dbg" does not match ...
3
votes
2answers
278 views

bash completion in Posix mode

I would like to use an interactive Posix bash shell but the autocomplete feature doesn't work. When I type the Tab character it simply prints a tab. The tab completion works only when I'm in a ...
9
votes
1answer
467 views

What is the point of using multiple exclamation marks in sed?

POSIX sed documentation said: A function can be preceded by one or more '!' characters, in which case the function shall be applied if the addresses do not select the pattern space. Zero or ...
0
votes
2answers
135 views

Grep for regex in basename but return wholename

So say I have a list of files in a text file: ... /foo/barfoo /bar/foo/foobar /foobar/bar/foo ... I have a script that will search through this text file and, much like the locate command, I want ...
4
votes
1answer
332 views

Posix command that moves cursor to specific position in terminal window

in school we have been assigned a homework in which we are suppose to print an ascii art into a terminal window. A input is data in format [x_coordinate, y_coordinate, char_ascii_value] (there is no ...
2
votes
1answer
97 views

POSIX shell scripting and performance tuning [closed]

Nowadays, I'm researching for performance tuning for shell scripting , And I have been prevented to POSIX shell scripting, However it's only a standard, But I think it's rathar than standard for do ...
5
votes
1answer
101 views

What are the 'n', 'l', '3pm' sections of the manual for?

An excerpt from the man man page: The default action is to search in all of the available sections following a pre-defined order ("1 n l 8 3 2 3posix 3pm 3perl 5 4 9 6 7" by default) What are ...
1
vote
2answers
222 views

Is it better to archive/move mail based on mtime or ctime?

I have been using a perl script to archive mail found here The script uses ctime to process and decide which month sub folder to place mail. In most cases this is fine since the ctime = mtime and ...
4
votes
3answers
358 views

When to use XPG* version of a command?

I occasionally do work on an older Solaris machine whose default version of grep is non-POSIX-compliant. This causes problems in my rc files because the default grep on the machine doesn't support ...
2
votes
1answer
208 views

I have a multi-line string that I need to iterate over, but I'm not using bash. Advice?

I'm using Dash because this is to run on my rPi. Bash is not an option. I'm rewriting a Bash script to work with Dash. I'm hoping to make it as POSIX-compliant (portable) as possible. The thing is ...
2
votes
1answer
159 views

Order between options and operands?

When using a utility program, we may specify options (and their option arguments) and/or operands. In most cases (in the sense of conforming to some standard (POSIX?)) does the order between ...
1
vote
1answer
256 views

Will `mv` ever have the ability to create directories?

This question asks for the best way to create a directory when using mv if it doesn't exist. My question is why isn't this an inbuilt feature of mv? Is there some fundamental reason due to which this ...
1
vote
1answer
214 views

What, as examples, can produce a POLLNVAL?

The reference about poll() just says “The specified fd value is invalid. This flag is only valid in the revents member; it shall ignored in the events member.”. That's not clear (at least to me): if ...
1
vote
1answer
219 views

Multithreading in Mail server (Postfix)

I need to perform multithreading on postfix mail server. I read about POSIX multithreading but could it be linked to postfix smtp server and if yes then how? System Specification: ubuntu 14.04 LTS and ...
3
votes
0answers
96 views

find printf switch POSIX alternative

I'd like to rewrite these 2 command so they will use only POSIX-complaint switches: find "$TARGET_DIR" -maxdepth 1 -type d -printf '(DIR) %f\n' find "$TARGET_DIR" -maxdepth 1 -type f -printf '%s %f ...
1
vote
0answers
69 views

OS X Yosemite is SUS - Single Unix Specification 3 certified. But what posix standard is it compliant to? the latest one is 2008

I'm confused. Is SUS compliance the same as POSIX compliance? Is yosemite compliant to the latest standards, what years exactly?
11
votes
4answers
5k views

Use #!/bin/sh or #!/bin/bash for Ubuntu-OSX compatibility and ease of use & POSIX

I know that I can use either as the first line of scripts to invoke the desired shell. Would #!/bin/sh be recommended if compatibility with all unix systems is an absolute requirement? In my case ...
10
votes
1answer
363 views

regarding portable sed -e… d b or ! b?

In this edit Stéphane Chazelas POSIXifies (again) my sed formatting by inserting an -expression break and another -expression statement. Now, I might just ask him why in the comments, I suppose, but ...
1
vote
0answers
57 views

POSIX description of cp -R

I just became really confused by the implementation of bash's cp -R command compared to how POSIX words what should happen Given the posix definition, I would expect cp -R srcDir existingDestDir to ...
5
votes
1answer
258 views

Why does 'find -exec cmd {} +' need to end in '{} +'?

Preface: I understand the difference between -exec {} \; & -exec {} +. I also don't have a problem as such, I am just curious about the semantics of find. When ending the -exec argument with + ...
3
votes
1answer
99 views

Is field splitting and filename expansion turn off in RHS of variable assignment portable?

In most POSIX compliant shell like bash. ksh, dash, mksh, pdksh, when variable assignment occur, field splitting and filename expansion (and brace expansion if the shell supports) are not performed in ...
-2
votes
1answer
499 views

Regular expression in unzip files argument not working

I'm trying to view the contents of a zip archive using an extremely simple regular expression. This works: rmorton@Rockette:~$ unzip -l Downloads/WeiDU-Linux-236.zip "*/i386/tolower" "*/i386/weidu" ...
10
votes
2answers
1k views

Where can I find official POSIX and UNIX documentation?

I am looking for official documents on all POSIX standards and specifications. I would like to be able t read the docs to get a better understanding of UNIX systems and how they work at a low level. ...
10
votes
3answers
1k views

POSIX compliant way to work with a list of filenames possibly with whitespace

I have seen Bash scripting guides suggesting the use of array for working with filenames containing whitespace. DashAsBinSh however suggests that arrays are not portable so I am looking for a POSIX ...
3
votes
2answers
787 views

Is there a specific reason why iptables would return an exit code of 3 (instead of 1?) when executed without sufficient privileges?

I simply forgot to use sudo: usr@arch ~[0] $ iptables -L iptables v1.4.21: can't initialize iptables table `filter': Permission denied (you must be root) Perhaps iptables or your kernel needs to be ...
1
vote
1answer
462 views

open() return new file descriptor posix [closed]

I have to set the return values for open() in posix. How do I return "the new file descriptor" as it is said in the Linux man pages: RETURN VALUE open(), openat(), and creat() return the new ...
10
votes
2answers
1k views

Is it OK to use “.” to run files instead of source - in .bashrc in Ubuntu and OS X?

OK, so source runs the script in the current shell and . separately, as detailed in running script with ". " and with "source " for example, but, specifically, in my .bashrc file, ...
3
votes
2answers
140 views

How is it possible to execute a command with an unknown number of arguments in a POSIX shell?

I want to search for multiple words inside the current directory. To accomplish this I use something like this. grep -e "word1" -e "word2" -R . This works fine. Taking this one step further, I ...
3
votes
1answer
224 views

Single or double brackets and portability

I have found some very good answers here on the differences between [ and [[ in 'if' statements. For specific named shells, it seems to be a good idea to use [[ over [ (and it is faster, too). I'm ...
4
votes
3answers
15k views

linux command to check POSIX message queue

We can check the details of system V message queue with the help of ipcscommand. Is there any command to check POSIX message queue in Linux?
2
votes
1answer
184 views

Process IDs range

On GNU/Linux system I seen only positive PIDs, but when kernel panic occured I seen info about process with PID=0. What's it? On Minix 3 I seen processes with negative PIDs. Minix is POSIX-compatible ...
6
votes
4answers
250 views

Is it shell portable to run a command on the same line after variable assignment?

Is there any standard that covers the portability of running a command after variable assignment on the same line? APPLE="cider" echo hi How portable is something like that? Where will it work and ...
3
votes
3answers
309 views

Interactive command usage reference: do you generally have that on Unix?

The question of why some commands rely on manpages whereas others rely on something like the --help flag for providing command usage reference is not new. There is usually a difference in scope ...
28
votes
1answer
3k views

When and how was the double-dash (--) introduced as an end of options delimiter in Unix/Linux?

I don't think the shell/utilities in historical Unix nor in something as "recent" as 4.4BSD supported using a double-dash(or two consecutive hyphens) as an end of options delimiter. With FreeBSD, you ...
3
votes
2answers
2k views

Replace a pattern in a file with a long string

I'm writing a little shell script to generate a directory listing. To make the output easily customizable, the script just builds a HTML-table and than should replace a specific token in a template ...
6
votes
1answer
337 views

Does Posix require any devices?

Does Posix require any devices? For example, /dev/urandom, /dev/zero or /dev/null? I suspect not because of non-*nix OSes, but wanted to ask for completeness.
2
votes
1answer
1k views

Removing non-printable characters using POSIX sed

Files created with roff and other "old-school" tools (for example man pages on many Unix systems) generate bold and underlined text in minimalistic terminals using tricks involving non-printable ASCII ...
7
votes
3answers
594 views

`/proc/$PID/cwd` : is there a POSIX equivalent?

Linux has a /proc directory and file‑system, which as far as I can tell, is not part of POSIX. In each /proc/$PID subdirectories, is a symbolic link, cwd, pointing to the actual working directory of ...
23
votes
4answers
1k views

Is the shell permitted to optimize out useless terminating commands?

If a shell is asked to perform a probably useless (or partially useless) command known to terminate, such as cat hugeregularfile.txt > /dev/null, can it skip that command's execution (or execute a ...
18
votes
2answers
777 views

explanation on chown(1) POSIX spec

The POSIX spec for the chown utility mentions in its rationale section about the chown user:group syntax (formerly chown user.group) (emphasis mine): The 4.3 BSD method of specifying both owner ...
3
votes
4answers
493 views

Protected environment variables?

Are there names of environment variables that cannot be overwritten by the user/a call to setenv? As I understand from POSIX1.2008, any process may edit the environment block, but must avoid ...
12
votes
5answers
3k views

What is meant by “a system call” if not the implementation in the programing language?

I would like to understand the term "system call". I am familiar that system calls are used to get kernel services from a userspace application. The part i need clarification with is the difference ...
5
votes
2answers
404 views

How exactly does `if $cmd ; then $cmd ; fi` differ from `$cmd && $cmd`?

In an answer to another very good question I made the following assertion: According to my reading of the POSIX specs, the use of one or the other makes no difference from a parsing standpoint. ...
0
votes
1answer
445 views

bash completion on posix mode [duplicate]

I would like to use an interactive posix bash shell but the autocompletion feature doesn't work. When i type the tab character it simply prints a tab. The tab completion only works when i'm on a non ...
5
votes
1answer
251 views

Where is $_ defined by POSIX?

In the comments to the accepted answer to this Unix & Linux StackExchange question, it is stated that $_ is "one of only some 7 special parameters defined by POSIX". I can't find that definition ...
2
votes
3answers
158 views

Why are POSIX Find Parameters Different from Other Program styles?

Why is a parameter in the POSIX find command added with a single hyphen for multi-character parameter names, while most other programs use single hyphen to indicate multiple single-character flags, ...
4
votes
2answers
490 views

Is the double dash still the posix standard for long switches?

I've read several question about double dash: Single dashes - for single-character options, but double dashes -- for words? What does -- (double-dash) mean? (also known as “bare double dash”) ...
9
votes
2answers
558 views

Which is the most portable of sed, awk, perl and sh?

Can someone put these tools in order of portability? Which of these is certain to be found on even the most minimal *nix systems? Is any of them 100% sure to be present? My guess is that the order is ...