1.9 KiB
Wild Cards
Use *, ? (for one char), and [abc] for a series of options. Example:
$ ls [abc]*
More commands on one line
Use ; $ date;who
Redirection of Standard output/input
, >>, <
Examples:
$ sort < filename > sorted_names
Pipes
A pipe is nothing but a temporary storage place where the output of one command is stored and then passed as the input for second command.
Processes and PID
An instance of running command is called process and the number printed by shell is called process-id (PID), this PID can be use to refer specific running process.
ps - show current running kill {PID} - kill process kill 0 - stop all processes except shell & - background process ps aux - display the owner of the processes along with the processes ps -ag - get information of all running processes ps ax | grep processes-you-want-to-see top - see currently running processes and other information like memory and CPU pstree - display a tree of processes
Useful Cmds:
List size of folders $ du -sh *
Print calendar: $ cal
Writing and creating a file: $ cat > NEWFILE
--- write here --- ^D
De-bug Shell Script
Use -v and -x option: $ sh option SCRIPT $ bash option SCRIPT
Local and Global Variables
Whenever you type: $ /bin/bash You start a new shell where the previous variables will be forgotten (local variables). To make variables global, you can do: $ export VARIABLE-NAME Before changing shell.
Conditional Execution
The control operators are && (AND) and || (OR). $ rm myf && echo "File is removed successfully" || echo "File is not removed"
Functions
$ SayHello() { echo "Hello $LOGNAME, Have nice computing" return } To execute this SayHello() function just type it name as follows: $ SayHello