DJack Software - Technical Information

Easy Command-Line Introduction

Posted: 9 Feb 2005

Among the many wonders of Linux is the ability to customize how you, individually, like to do things. Many people like the ability to use the mouse to point and click on a graphical interface. This is to say, they like to use a window manager like Gnome or KDE. Another option, however, is to use the command line. Contrary to popular belief, the command line is not difficult to use. In some cases, it takes the complication out of things. I'd like to run through a bunch of common commands. We'll look at what each does and how to use each one.

Find the TERMINAL PROGRAM icon in your Kicker bar and click on it:

This opens your terminal window so you can try these babies out. Also, after you type each command, press the ENTER key to run it. Here is a list of the common commands:

Command: ls

Usage: ls

Explanation: Displays contents of the current directory.

Sample Output:

[1702][smorris@linux:~/home]$ ls bin Desktop Documents hardware.txt icons.lst public_html [1702][smorris@linux:~/home]$

Command: mkdir

Usage: mkdir <dirname>

Explanation: Makes a subdirectory in the current directory.

Sample Output:

[1702][smorris@linux:~/home]$ mkdir temp [1808][smorris@linux:~/home]$

Command: rmdir

Usage: rmdir <directory>

Explanation: Removes a directory.

Sample Output:

[1834][smorris@linux:~]$ rmdir temp [1834][smorris@linux:~]$

Command: cd

Usage: cd <new directory>

Explanation: Changes the current directory to a new one.

Sample Output:

[1834][smorris@linux:~]$ cd home [1834][smorris@linux:~/home]$

Command: pwd

Usage: pwd

Explanation: Shows the present working directory.

Sample Output:

[1808][smorris@linux:~/home]$ pwd /home/smorris/home [1825][smorris@linux:~/home]$

Command: cp

Usage: cp <source file> <target file>

Explanation: Copies a file from its current location to somewhere else.

Sample Output:

[1938][smorris@linux:~/home]$ cp hardware.txt mystuff.txt [1938][smorris@linux:~/home]$

Command: mv

Usage: mv <source file> <target file>

Explanation: Moves a file from its current location to somewhere else.

Sample Output:

[1938][smorris@linux:~/home]$ mv hardware.txt mystuff.txt [1938][smorris@linux:~/home]$

Command: rm

Usage: rm <filename>

Explanation: Removes a file.

Sample Output:

[1938][smorris@linux:~/home]$ rm mystuff.txt [1939][smorris@linux:~/home]$

Note: The result of the 'rm' command is permanent. You cannot undo it, so be very careful with this command.

Command: ps

Usage: ps aux

Explanation: Shows a list of the current running processes.

Sample Output:

[1839][smorris@linux:~]$ ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 596 80 ? S Jan27 0:01 init [5] root 3 0.0 0.0 0 0 ? S Jan27 0:02 [events/0] root 4 0.0 0.0 0 0 ? S Jan27 0:00 [khelper] root 5 0.0 0.0 0 0 ? S Jan27 0:00 [netlink/0] root 6 0.0 0.0 0 0 ? S Jan27 0:00 [kacpid] root 23 0.0 0.0 0 0 ? S Jan27 0:19 [kblockd/0] root 36 0.0 0.0 0 0 ? S Jan27 0:00 [aio/0] root 35 0.0 0.0 0 0 ? S Jan27 0:12 [kswapd0] root 618 0.0 0.0 0 0 ? S Jan27 0:00 [kseriod] root 1643 0.0 0.0 0 0 ? S Jan27 0:00 [ata/0] root 1645 0.0 0.0 0 0 ? S Jan27 0:00 [scsi_eh_0] root 1646 0.0 0.0 0 0 ? S Jan27 0:00 [scsi_eh_1] root 1655 0.0 0.0 0 0 ? S Jan27 0:02 [reiserfs/0] root 2168 0.0 0.0 0 0 ? S Jan27 0:00 [khubd] root 2224 0.0 0.0 1360 256 ? S Jan27 0:00 udevd root 2484 0.0 0.0 1432 320 ? S Jan27 0:00 [hwscand] smorris 14651 0.0 0.3 4248 1840 pts/3 Ss 18:39 0:00 /bin/bash smorris 14661 0.0 0.1 2372 704 pts/3 R+ 18:39 0:00 ps aux [1839][smorris@linux:~]$

Note: You will see much more output than this. I had to cut it off because it was too long to put all of it here.

Command: kill

Usage: kill <process id>

Explanation: Terminates a process.

Sample Output:

[1848][smorris@linux:~]$ kill 14988 [1848][smorris@linux:~]$

Note: The process ID can be found using the 'ps' command, above.

Command: uptime

Usage: uptime

Explanation: Shows how long it has been since the computer was last rebooted.

Sample Output:

[1848][smorris@linux:~]$ uptime 6:54pm up 11 days 21:36, 4 users, load average: 0.10, 0.14, 0.10 [1854][smorris@linux:~]$

Command: date

Usage: date

Explanation: Shows the current system time and date.

Sample Output:

[1854][smorris@linux:~]$ date Tue Feb 8 19:20:07 CST 2005 [1920][smorris@linux:~]$

Command: ifconfig

Usage: /sbin/ifconfig

Explanation: Shows your IP address and network adapter information.

Sample Output:

[1825][smorris@linux:~/home]$ /sbin/ifconfig eth0 Link encap:Ethernet HWaddr 00:0B:DB:C5:E1:AC inet addr:192.168.0.106 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::20b:dbff:fec5:e1ac/64 Scope:Link UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2911835 errors:0 dropped:0 overruns:0 frame:0 TX packets:1878982 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2017894151 (1924.4 Mb) TX bytes:199806447 (190.5 Mb) Base address:0xdf40 Memory:feae0000-feb00000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:2499998 errors:0 dropped:0 overruns:0 frame:0 TX packets:2499998 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:584776793 (557.6 Mb) TX bytes:584776793 (557.6 Mb) [1827][smorris@linux:~/home]$

Note: Look at the second line. After the 'inet addr:' there is a group of numbers and periods. This is the IP address. In this example, the IP address is 192.168.0.106.

Command: ping

Usage: ping <host or ip>

Explanation: Sends a small signal to a remote server, which answers. This is very useful for testing an Internet connection.

Sample Output:

[1827][smorris@linux:~/home]$ ping google.com PING google.com (216.239.39.99) 56(84) bytes of data. 64 bytes from 216.239.39.99: icmp_seq=1 ttl=239 time=32.1 ms 64 bytes from 216.239.39.99: icmp_seq=2 ttl=239 time=32.4 ms 64 bytes from 216.239.39.99: icmp_seq=3 ttl=239 time=33.0 ms 64 bytes from 216.239.39.99: icmp_seq=4 ttl=239 time=33.5 ms --- google.com ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3001ms rtt min/avg/max/mdev = 32.103/32.792/33.556/0.577 ms [1832][smorris@linux:~/home]$

Note: To stop the pinging, press CTRL+C.

Command: top

Usage: top

Explanation: Displays a report of the currently running processes. This report updates every 3 seconds.

Sample Output:

top - 18:45:24 up 11 days, 21:27, 4 users, load average: 0.11, 0.07, 0.08 Tasks: 121 total, 2 running, 119 sleeping, 0 stopped, 0 zombie Cpu(s): 2.6% us, 0.8% sy, 0.0% ni, 94.8% id, 1.5% wa, 0.3% hi, 0.0% si Mem: 514496k total, 509096k used, 5400k free, 75768k buffers Swap: 1959920k total, 277912k used, 1682008k free, 143512k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 17509 root 16 0 204m 56m 146m R 1.7 11.3 21:33.88 X 13480 smorris 16 0 36696 23m 29m S 0.7 4.6 0:12.08 kate 14650 smorris 15 0 30364 14m 26m S 0.2 2.9 0:00.62 konsole 17647 smorris 16 0 50016 26m 34m S 0.1 5.3 2:25.75 kicker 8616 smorris 15 0 66588 38m 32m S 0.1 7.6 0:33.73 firefox-bin 8371 lp 16 0 6876 1420 3740 S 0.0 0.3 1:54.78 cupsd 17640 smorris 15 0 27720 12m 24m S 0.0 2.4 0:44.25 kwin 17644 smorris 15 0 25440 9648 23m S 0.0 1.9 0:03.80 khotkeys 1 root 16 0 596 80 452 S 0.0 0.0 0:01.33 init 2 root 34 19 0 0 0 S 0.0 0.0 0:04.60 ksoftirqd/0 3 root 5 -10 0 0 0 S 0.0 0.0 0:02.77 events/0 4 root 5 -10 0 0 0 S 0.0 0.0 0:00.02 khelper 5 root 5 -10 0 0 0 S 0.0 0.0 0:00.06 netlink/0 6 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kacpid 23 root 5 -10 0 0 0 S 0.0 0.0 0:19.39 kblockd/0 36 root 6 -10 0 0 0 S 0.0 0.0 0:00.00 aio/0 35 root 15 0 0 0 0 S 0.0 0.0 0:12.40 kswapd0 618 root 24 0 0 0 0 S 0.0 0.0 0:00.00 kseriod 1643 root 6 -10 0 0 0 S 0.0 0.0 0:00.00 ata/0

Note: Press SHIFT+M to sort by memory. Press SHIFT+P to sort by CPU usage. Press CTRL+C to exit.

There are many, many commands that I could have listed here. These are some of the basic everyday ones. For a more in-depth look at using the command line, there are many tutorial sites available, such as this one.

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