Simple completion using function _mycompletion() { local command_name="$1" # not used in this example local current_word="$2" local previous_word="$3" # not used in this example # COMPREPLY is an array which …

Compare two files from the web The following compares two files with diff using process substitution instead of creating temporary files. diff <(curl http://www.example.com/page1) <(curl http://www.example.com/page2) Feed a while loop …

Dynamic scoping in action Dynamic scoping means that variable lookups occur in the scope where a function is called, not where it is defined. $ x=3 $ func1 () { …

Parameter DetailsEXPRESSION Expression to evaluate Simple arithmetic with (( )) #!/bin/bash echo $(( 1 + 2 )) Output: 3 # Using variables #!/bin/bash var1=4 var2=5 ((output=$var1 * $var2)) printf "%d\n" …

Math using dc dc is one of the oldest programs on Unix. It uses reverse polish notation, which means that you first stack numbers, then operations. For example 1+1 iswritten …

Quick Reference Interaction with the history # List all previous commands history # Clear the history, useful if you entered a password by accident history -c Event designators # Expands …

To parse lots of parameters, the prefered way of doing this is using a while loop, a case statement, and shift.shift is used to pop the first parameter in the …

The -e conditional operator tests whether a file exists (including all file types: directories, etc.). if [[ -e $filename ]]; then echo "$filename exists" fi There are tests for specific …

Double quotes for variable and command substitution Variable substitutions should only be used inside double quotes. calculation='2 * 3' echo "$calculation" # prints 2 * 3 echo $calculation # prints …

Execute command with here document ssh -p 21 example@example.com <<EOF echo 'printing pwd' echo "\$(pwd)" ls -a find '*.txt' EOF $ is escaped because we do not want it to …