You cannot have spaces around the = sign. When you write: STR = “foo” bash tries to run a command named STR with 2 arguments (the strings = and foo) When you write: STR =foo bash tries to run a command named STR with 1 argument (the string =foo) When you write: STR= foo bash … Read more
In cross-platform, lowest-common-denominator sh you use: #!/bin/sh value=`cat config.txt` echo “$value” In bash or zsh, to read a whole file into a variable without invoking cat: #!/bin/bash value=$(<config.txt) echo “$value” Invoking cat in bash or zsh to slurp a file would be considered a Useless Use of Cat. Note that it is not necessary to … Read more
From help set : -e Exit immediately if a command exits with a non-zero status. But it’s considered bad practice by some (bash FAQ and irc freenode #bash FAQ authors). It’s recommended to use: trap ‘do_something’ ERR to run do_something function when errors occur. See http://mywiki.wooledge.org/BashFAQ/105
set -x or set -o xtrace expands variables and prints a little + sign before the line. set -v or set -o verbose does not expand the variables before printing. Use set +x and set +v to turn off the above settings. On the first line of the script, one can put #!/bin/sh -x (or … Read more
Revised Answer (Feb 12, 2014) the_world_is_flat=true # …do something interesting… if [ “$the_world_is_flat” = true ] ; then echo ‘Be careful not to fall off!’ fi Original Answer Caveats: https://stackoverflow.com/a/21210966/89391 the_world_is_flat=true # …do something interesting… if $the_world_is_flat ; then echo ‘Be careful not to fall off!’ fi From: Using boolean variables in Bash The reason … Read more
What is sh? sh (or the Shell Command Language) is a programming language described by the POSIX standard. It has many implementations (ksh88, Dash, …). Bash can also be considered an implementation of sh (see below). Because sh is a specification, not an implementation, /bin/sh is a symlink (or a hard link) to an actual … Read more
You can use Marcus’s answer (* wildcards) outside a case statement, too, if you use double brackets: string=’My long string’ if [[ $string == *”My long”* ]]; then echo “It’s there!” fi Note that spaces in the needle string need to be placed between double quotes, and the * wildcards should be outside. Also note … Read more