more bash examples

shell_scripts/lessons/TRICKS.md

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+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 *
+
+