If you are developing an application for Linux desktop and would like to automatically find out more information about system, use the following commands in shell scripts to gather information about system. Before applying a command you must know how to use the command effectively in Shell. Here we are explaing basich linux system commands and their usage.
This command will help you to find out your present working direcotry.
[root@l3admins ~]# pwd /root [root@l3admins ~]#
The kernel maintains the current (unqualified) hostname of the system. Before trying to set your hostname, it’s important to know how to tell when you’ve got it right. Here are a few of the numerous ways to obtain it:
[root@l3admins ~]# hostname l3admins [root@l3admins ~]#
This will display the login name like admin,root or your user name.
[root@l3admins ~]# whoami root [root@l3admins ~]#
This command will display all the informations about a user like user ID, memeber of which Group and prints other user identity information
[root@l3admins ~]# id root uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel) context=root:system_r:unconfined_t:SystemLow-SystemHigh [root@l3admins ~]#
This command will display the current date and timezone of your machine
[root@l3admins ~]# date Tue Jan 4 01:01:14 PST 2011 [root@l3admins ~]#
Its a command which conveys so many informations like load, number of users logged in, Uptime for the system.
[root@l3admins ~]# w 01:46:06 up 59 min, 3 users, load average: 0.00, 0.00, 0.04 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT root :0 - 00:49 ?xdm? 25.17s 0.39s /usr/bin/gnome-session root pts/1 :0.0 00:50 43:23 0.12s 0.12s bash root pts/2 192.168.10.1 01:03 0.00s 0.16s 0.01s w [root@l3admins ~]#
This is a user information lookup program, Finger displays the userâs login name, real name, terminal name and write status (as a ââ*ââ after the terminal name if write permission is denied), idle time, login time, office location and office phone number.
[root@l3admins ~]# finger root Login: root Name: root Directory: /root Shell: /bin/bash On since Tue Jan 4 00:49 (PST) on :0 (messages off) On since Tue Jan 4 00:50 (PST) on pts/1 from :0.0 49 minutes 26 seconds idle On since Tue Jan 4 01:03 (PST) on pts/2 from 192.168.10.1 New mail received Fri Dec 31 02:30 2010 (PST) Unread since Sun Dec 5 08:36 2010 (PST) No Plan. [root@l3admins ~]#
This command will bring you the information about the last loggedin user.
[root@l3admins ~]# last root pts/2 192.168.10.1 Tue Jan 4 01:03 still logged in root pts/1 :0.0 Tue Jan 4 00:50 still logged in root :0 Tue Jan 4 00:49 still logged in root :0 Tue Jan 4 00:49 - 00:49 (00:00) reboot system boot 2.6.18-194.el5 Tue Jan 4 06:18 (-4:-23)
This command will give you the information about the last bad (unsuccessful) login attempts to the machine.
[root@l3admins ~]# lastb root ssh:notty 192.168.10.1 Tue Jan 4 01:58 - 01:58 (00:00) root ssh:notty 192.168.10.1 Tue Jan 4 01:58 - 01:58 (00:00) btmp begins Tue Jan 4 01:58:31 2011 [root@l3admins ~]#
Memory info (in kilobytes). “Shared” memory is the memory that can be shared between processes (e.g., executable code is “shared”). “Buffered” and “cashed” memory is the part that keeps parts of recently accessed files – it can be shrunk if more memory is needed by processes.
[root@l3admins ~]# free total used free shared buffers cached Mem: 1035108 655116 379992 0 88648 410024 -/+ buffers/cache: 156444 878664 Swap: 2096472 0 2096472 [root@l3admins ~]#