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

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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 ...
4
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1answer
69 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 ...
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0answers
14 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 ...
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2answers
137 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 ...
8
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1answer
192 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 ...
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2answers
44 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
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1answer
31 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 ...
47
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2answers
6k views

$VAR vs ${VAR} and to quote or not to quote

I can write VAR=$VAR1 VAR=${VAR1} VAR="$VAR1" VAR="${VAR1}" the end result to me all seems about the same. Why should I write one or the other? are any of these not portable/POSIX?
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1answer
53 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 ...
4
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1answer
57 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
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1answer
32 views

read reading input devided by spaces

How can I read in POSIX bash input like this: <name>,<tag1> <tag2> <tag3>… I tried while read line;do done but this wants newlines, all I have is spaces. (Is IFS solution? ...
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2answers
216 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 ...
2
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1answer
69 views

uname -n vs hostname

What is the difference between uname -n and hostname? Are there any real differences in what they return? Are there any differences in availability on different OSes? Is one of them included in POSIX ...
3
votes
3answers
60 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
58 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 ...
30
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1answer
2k views

Does 'rm .*' ever delete the parent directory?

The expression .* is expanded by bash to include the current and parent directories: $ ls -la total 2600 drwxrwxrwx 2 terdon terdon 2162688 Sep 10 16:22 . drwxr-xr-x 142 terdon terdon 491520 Sep ...
2
votes
1answer
50 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
92 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
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1answer
54 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
73 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
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0answers
51 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 ...
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0answers
54 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?
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4answers
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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
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1answer
304 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 ...
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0answers
42 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 ...
53
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3answers
11k views

What exactly is POSIX?

I see POSIX mentioned often and everywhere, and I had assumed it to be the baseline UNIX standard.. until I noticed the following excerpt on a Wikipedia page: The Open Group The Open Group is ...
5
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1answer
154 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 + ...
34
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7answers
2k views

Is test or [ or [[ more portable both between bash shells and between other shells?

I see I can do $ [ -w /home/durrantm ] && echo "writable" writable or $ test -w /home/durrantm && echo "writable" writable or $ [[ -w /home/durrantm ]] && echo ...
0
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1answer
36 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 ...
10
votes
4answers
9k views

find -exec in bash script with variable expansion

I'm trying to run a command similar to the one below in a bash script. It should search through all subfolders of $sourcedir and copy all files of a certain type to the root level of $targetdir. ...
-2
votes
1answer
151 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" ...
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2answers
669 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. ...
8
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3answers
470 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 ...
2
votes
2answers
320 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
184 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
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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
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2answers
54 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 ...
26
votes
4answers
3k views

difference between “function foo() {}” and “foo() {}”

I can define bash functions using or omitting the function keyword. Is there any difference? #!/bin/bash function foo() { echo "foo" } bar() { echo "bar" } foo bar Both calls to functions ...
2
votes
1answer
95 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 ...
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3answers
9k 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
95 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 ...
5
votes
4answers
175 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
239 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 ...
23
votes
1answer
986 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 ...
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2answers
1k 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
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1answer
212 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.
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votes
1answer
4k views

How do I use grep to find a text string in files in sub folders of a parent folder without -r switch

I'm using Solaris 10 and have two grep versions one in /usr/bin and one in /usr/xpg4/bin. I have been searching for an answer on how to search for text within files within sub folders of a parent ...
2
votes
1answer
770 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 ...
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3answers
403 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 ...
22
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 ...