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linux:scripts:basics

Script

Commands

Command Function
#!/bin/bash
or
#!/bin/sh
shebang
VAR=var set VAR to var
$VAR inserts var whereever $VAR is placed
case - esac inserts case
if [ “var” == “var” ]; then fi inserts if

if conditions

Operator Description
-eq Returns true if two numbers are equivalent
-lt Returns true if a number is less than another number
-gt Returns true if a number is greater than another number
== Returns true if two strings are equivalent
!= Returns true if two strings are not equivalent
! Returns true if the expression is false
-d Check the existence of a directory
-e Check the existence of a file
-r Check the existence of a file and read permission
-w Check the existence of a file and write permission
-x Check the existence of a file and execute permission
-z string is null, that is, has zero length
-n string is not null.

https://tldp.org/LDP/abs/html/comparison-ops.html

Troubleshooting

Interpreter error

Problem:

Running your script prompts interpreter error

Fix:

Open your script with vi and execute the following

 :set fileformat=unix 

Not enough rights

Problem:

Running your script requires more rights

Fix:

Make your script executable with the following command

chmod +x [scriptname].sh



linux/scripts/basics.txt · Last modified: 2021/01/07 14:55 by lunetikk