Frequent Questions

… or an introductory guide to robust filename handling and other string passing in shell scripts. I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some ...

Is using a while loop to process text generally considered bad practice in POSIX shells? As Stéphane Chazelas pointed out, some of the reasons for not using shell loop are conceptual, reliability, ...

I consistently see answers quoting this link stating definitively "Don't parse ls!" This bothers me for a couple of reasons: It seems the information in that link has been accepted wholesale with ...

I have heard that printf is better than echo. I can recall only one instance from my experience where I had to use printf because echo didn't work for feeding some text into some program on RHEL 5.8 ...

The old advice used to be to double-quote any expression involving a $VARIABLE, at least if one wanted it to be interpreted by the shell as one single item, otherwise, any spaces in the content of $...

If you've been following unix.stackexchange.com for a while, you should hopefully know by now that leaving a variable unquoted in list context (as in echo $var) in Bourne/POSIX shells (zsh being the ...

I often see tutorials online that connect various commands with different symbols. For example: command1 | command2 command1 & command2 command1 || command2 command1 && command2 ...

This question is inspired by Why is using a shell loop to process text considered bad practice ? I see these constructs for file in `find . -type f -name ...`; do smth with ${file}; done and for ...

$ ls -l /tmp/test/my\ dir/ total 0 I was wondering why the following ways to run the above command fail or succeed? $ abc='ls -l "/tmp/test/my dir"' $ $abc ls: cannot access '"/tmp/test/my': No such ...

I wrote a regular expression which works well in a certain program (grep, sed, awk, perl, python, ruby, ksh, bash, zsh, find, emacs, vi, vim, gedit, …). But when I use it in a different program (or on ...

When looking for the path to an executable or checking what would happen if you enter a command name in a Unix shell, there's a plethora of different utilities (which, type, command, whence, where, ...

I find myself constantly looking up the syntax of find . -name "FILENAME" -exec rm {} \; mainly because I don't see how exactly the -exec part works. What is the meaning of the braces, the backslash ...

I think these terms almost refer to the same thing, when used loosely: terminal shell tty console What exactly does each of these terms refer to?

When I sum up the sizes of my files, I get one figure. If I run du, I get another figure. If I run du on all the files on my partition, it doesn't match what df claims is used. Why are there so many ...

In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory, and how do directory permissions in Linux ...