Shell Script ?
- Shell script can take input from user, file and output them on screen
- Automating system administration task
- To automate some task of day-to-day life
- Save lots of times
- Userfule to create own/custom commands
Creating Code Snippets
Creating abbreviations in .vimrc
Abbreviations allow for a shortcut string to be used in place of longer string.Just open ~./vimrc and type a shortcut code you want.
abbr _sh #!/bin/bash
Using this abbreviations, we just need type _sh while in edit mode. On pressing the ENTER key after shortcut code, the full text for shebang is printed.
It’s easy let enjoy it !
Bringing color to the terminal
We create variables for some colors below :
RED="\033[31m" GREEN="\033[32m" BLUE="\033[34m" RESET="\033[0m"
We create file hello.sh, which makes use of these colors
#!/bin/sh a=12 until [ $a -lt 10 ] do echo $a a=expr $a + 1' done
The break Statement
The following break statement is used to come out of a loop
#!/bin/sh a=0 while [ $a -lt 10 ] do echo $a if [ $a -eq 5 ] then break fi a='expr $a + 1' done
Result is :
0 1 2 3 4 5
Here n specifies the nth enclosing loop to the exit from.
dev/null to send unwanted output program
$ls > dev/null
Output of above command is not shown on screen its send to this special file.
Regular Expressions with SED
SED stands for stream editor.
The sed General Syntax
patten is a regular expression and action is one of these command following.
p: prints the line d: delete the line s/pattern1/parttern2/ : Substitutes the first occurrence of pattern1 with pattern2
For details you can reference link below :
tutorial point shell scripting : regular expression
This is some stuff hope it help full for you to start with bash shell, in the next post I’ll write some scirpts we mosty use for administrators.