shell - Bash regex =~ operator - Stack Overflow
Oct 18, 2013 · The =~ operator is a regular expression match operator. This operator is inspired by Perl's use of the same operator for regular expression matching. The [[ ]] is treated specially by bash; consider that an augmented version of [ ] construct: [ ] is actually a shell built-in command, which, can actually be implemented as an external command.
bash - What are the special dollar sign shell variables ... - Stack ...
Sep 14, 2012 · This is on a current (year 2016) version of Bash, via Slackware 14.2. Whether $0 does include a path or not depends on how you ran the script in the first place. If you executed "./mytry.sh" that's what you will see in $0. If you entered "~/mytry.sh" you will see the full path (because the shell will have expanded ~).
bash - What is the purpose of "&&" in a shell command? - Stack …
Oct 27, 2021 · In shell, when you see. $ command one && command two. the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash. It intends to prevent the running of …
Meaning of $? (dollar question mark) in shell scripts
Aug 1, 2019 · echo $? # echoes 0. false. echo $? # echoes 1. From the manual: (acessible by calling man bash in your shell) Expands to the exit status of the most recently executed foreground pipeline. By convention an exit status of 0 means success, and …
bash - Shell equality operators (=, ==, -eq) - Stack Overflow
Bash variables are untyped so [[ "yes" -eq "no" ]] is equivalent to [[ "yes" -eq 0 ]] or [[ "yes" -eq "any_noninteger_string" ]] -- All True. The -eq forces integer comparison. The "yes" is interpreted as a integer 0; the comparison is True if the other integer is either 0 or the string result is 0.
linux - What does $@ mean in a shell script? - Stack Overflow
Apr 3, 2012 · In brief, $@ expands to the arguments passed from the caller to a function or a script. Its meaning is context-dependent: Inside a function, it expands to the arguments passed to such function. If used in a script (outside a function), it expands to the arguments passed to such script. $ cat my-script. #! /bin/sh.
arguments - What is $@ in Bash? - Stack Overflow
Oct 10, 2010 · 153. Just from reading that I would have never understood that "$@" expands into a list of separate parameters. Whereas, "$*" is one parameter consisting of all the parameters added together. If it still makes no sense, do this. Bash special parameters explained with four example shell scripts.
How to compare strings in Bash - Stack Overflow
Feb 10, 2010 · 1. In addition to previous answers, you can also use case statement to compare strings once you have a predefined set of values to choose from. For example, given that the user will provide an argument among these predefined values a or b or c or default once running the bash script, the following script demonstrates that. #!/bin/bash. case "$1 ...
How do I iterate over a range of numbers defined by variables in …
Oct 4, 2008 · Bash is a great shell and I use it interactively, but I don't put bash-isms into my scripts. Scripts might need a faster shell, a more secure one, a more embedded-style one. They might need to run on whatever is installed as /bin/sh, and then there are all the usual pro-standards arguments.
What do the -n and -a options do in a bash if statement?
This will show that -n tests the following argument and evaluates to true if it is not an empty string. In the documentation of test you will also see a the switch -e. This switch tests the following argument and evaluates to true if that argument is a file or directory that exists. More useful still is the -f switch which evaluates to true if ...