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Bash Scripting

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Bash Scripts

Reusuable sets of bash terminal commands can be created using bash scripts. Bash scripts can run any command that can be run in a terminal.

Bash Shebang

Bash script files start with #!/bin/bash. This special line tells the computer to use bash as the intepreter.

Bash script variables

Variables in a bash script can be set using the = sign, and accessed using $.

greeting="Hello" echo $greeting

Bash script comparison operators

In bash scripting, strings are compared using the == (Equal) and != (Not equal) operators.

#!bin/bash word1="Hello" word2="Hello" word3="hello" if [ $word1 == $word2 ] then echo "Strings are equal" fi if [ $word1 != $word3 ] then echo "Strings are not equal" fi

bash script read keyword

The read command can be used to prompt the user for input. It will continue to read user input until the Enter key is pressed.

Some prompt text can also be specified using -p with the read command.

#!bin/bash echo "Press Enter to continue" read read -p "Enter your name: " name

Bash Script Arguments

Arguments can be added to a bash script after the the script’s name. Once provided they can be accessed by using $(position in the argument list). For example, the first argument can be accessed with $1, the second with $2, the third with $3, etc.

#!/bin/bash # For a script invoked by saycolors red green blue # echoes red echo $1 # echoes green echo $2 # echoes blue echo $3

Bash Aliases

Aliases can be created using the keyword alias. They are used to create shorter commands for calling bash scripts. They can also be used to call bash scripts with certain arguments.

# For example, to create an alias that invokes the saycolor # script with the argument "green", the following syntax is used: alias saygreen='./ "green"'