shell-script-cheatsheet.md

Shell memo

Dev

#!/bin/sh (ou #!/bin/bash) # Header for a shell script

Variables

Declaration

variable=50
variable2=`cat file`

Input

read variable	# read user input

Usage

echo $variable # read a variable

Functions

Declaration

name(){
	cmds...
}

Call

name arg1 arg2 arg3...

Variables related to functions

• $# : argument number
• $0 : script file name
• $$ : PID du processus
• $i ($1 et +) : argument i
• $* : all arguments including script name
• $@ : all arguments without the script name
• shift n : shift arguments by n
• $? : exit code of a function

Conditions

Strings

$chaine1 = $chaine2 	# string equals
$chaine1 == $chaine2 	# string equals
$chaine1 != $chaine2 	# string not equals
-z $chaine1 		# empty string
-n $chaine1 		# not empty string

Numbers

$num1 -eq $num2 # =
$num1 -ne $num2	# !=
$num1 -lt $num2 # <
$num1 -le $num2 # <=
$num1 -gt $num2 # >
$num1 -ge $num2 # >=

Files

-a fichier # file exits
-d fichier # is a directory
-f fichier # is a regular file

And / Or / Not

[ condition1 ] && [ condition2 ]
[ condition1 ] || [ condition2 ]
[ ! condition1 ] 

Instructions

If

if [ condition ]
      then
        command1
      elif [ condition2 ]
        command2
      else
        default command
fi

While loop

while [ condition ]
    do
        commands
    done

For loop

for var in `cat files`
     do
      commands
     done

Case

case var in
	value1) instruction ;;
	value2) instruction ;;
	*) default instruction ;;
esac

Usefull commands