Linux commands for beginners part 2
Hi welcome to second part of Linux commands for beginners .If you are feeling comfortable with Linux commands you can surely easily understand the File Hierarchy System of Linux. Let’s start with commands which are very useful for any linux Administrator.
We will start with very powerful command which is Pipe represented by sign (|). Basically it is used for redirect the output of one command into another command. Syntax command1 | command2.
See the practical example of pipe(|) in below screenshot. First command is creating list of directory. Then output is piped and its counting number of line of output which is 11.
In second command we are piping output of directory listing and displaying first 5 lines of listing.
[fahmed@faraz var]# ls -l | wc -l 24 [fahmed@faraz var]# ls -l | head -5 total 88 drwxr-xr-x. 2 root root 4096 Oct 30 2014 account drwxr-xr-x. 15 root root 4096 Nov 5 2014 cache drwxr-xr-x. 2 root root 4096 Oct 30 2014 crash drwxr-xr-x. 2 root root 4096 Feb 2 2012 cvs
Now another kool command . I am going to change lower case letters to upper case letters in file and vice versa.
Syntax tr ‘a-z’ ‘A-Z’ < file-name. See the below image;
If you want to switch user then use su command
If you just type su and hit enter then it automatically switch to root.
If you have an ordinary user then type user-name.
Syntax su user-name.
To view and change the host/machine name we can use command hostname.
Syntax hostname new-hostname. (Note: you must be on root privilege.)
free command is used to view the memory status.
Syntax free [option].
Useful options are free –l (show the memory with detail),
free –m (show the memory with Mbs),
free –g (show the memory with Gbs).
[fahmed@faraz var]# free total used free shared buffers cached Mem: 22540264 2007488 20532776 0 234092 573932 -/+ buffers/cache: 1199464 21340800 Swap: 11530232 0 11530232 [fahmed@faraz var]# free -l total used free shared buffers cached Mem: 22540264 2007620 20532644 0 234096 573928 Low: 22540264 2007620 20532644 High: 0 0 0 -/+ buffers/cache: 1199596 21340668 Swap: 11530232 0 11530232 [fahmed@faraz var]# free -m total used free shared buffers cached Mem: 22011 1960 20051 0 228 560 -/+ buffers/cache: 1171 20840 Swap: 11259 0 11259 [fahmed@faraz var]# free -g total used free shared buffers cached Mem: 21 1 19 0 0 0 -/+ buffers/cache: 1 20 Swap: 10 0 10
du command is used to view the used disk space by any directory.
Syntax du dir-name.
Useful options are du –c (show the grand total),
du –h (human readable form),
du –s (show only a total size).
df is used to view the free disk space.
Syntax df dir-name.
Useful option is df –h (human readable form).
which command is used to show the full path of commands.
Syntax which command-name.
Whatis command is used to show the short description about command.
Syntax whatis command-name.
whereis command is used to locate the binary, source and manual pages.
Syntax whereis command-name.
I hope you have enjoyed tutorial. See you in next tutorial