Bash Cheat Sheet
Comparison operators
| Operator | Description | Operator | Description | |
| -eq | Is equal to | -n | Is not null | |
| -ne | Is not equal to | -z | Is null | |
| -gt | Is greater than | -r | file exists and is readable by the user | |
| -ge | Is greater than or equal to | -e | file exists | |
| -lt | Is less then | -f | file is a regular file (not directory or other special type) | |
| -le | Is less than or equal to | -s | file size is greater then 0 | |
| == | is equal to | -x | file is executable by the user | |
| != | is not equal to | -w | file is writable by the user | |
| < | Is less than | ! | negates the operator | |
| <= | Is less than or equal to | |||
| > | Is greater then | |||
| >= | Is greater than or equal to |
Variables for script arguments
| Variable | Description | Variable | Description | |
| $1 ... $n | Argument number | $# | Number of arguments | |
| $0 | Name of the file | $? | Return value (0 = ok, > 0 = error) | |
| $* | List of arguments |
Built in variables
| Variable | Description | Variable | Description | |
| $BASH | path to the bash binaries | $BASH_VERSION | version of bash | |
| $BASH_ENV | bash environment (used within the scripts) | $BASH_VERSINFO | more version details | |
| $$ | process id of the current script | $PATH | path variable | |
| $EDITOR | default editor | $UID | users id | |
| $EUID | effective user id | $FUNCNAME | name of the current function (executed from within the function) | |
| $GROUPS | groups to which the current user belongs |