Basic Unix Commands:

Some Basic UNIX Commands:
The UNIX operating system has for many years formed the backbone of the Internet, especially for large servers and most major university campuses. However, a free version of UNIX called Linux has been making significant gains against Macintosh and the Microsoft Windows 95/98/NT environments, so often associated with personal computers. Developed by a number of volunteers on the Internet such as the Linux group and the GNU project, much of the open-source software is copyrighted, but available for free. This is especially valuable for those in educational environments where budgets are often limited. 

 

UNIX commands can often be grouped together to make even more powerful commands with capabilities known as I/O redirection ( < for getting input from a file input and > for outputing to a file ) and piping using | to feed the output of one command as input to the next. Please investigate manuals in the lab for more examples than the few offered here.
The following charts offer a summary of some simple UNIX commands. These are certainly not all of the commands available in this robust operating system, but these will help you get started.  

 

Ten ESSENTIAL UNIX Commands
These are ten commands that you really need to know in order to get started with UNIX. They are probably similar to commands you already know for another operating system.

Command	Example	Description
1.     ls	ls ls -alF	Lists files in current directory List in long format
2.     cd	cd tempdir cd .. cd ~dhyatt/web-docs	Change directory to tempdir Move back one directory Move into dhyatt's web-docs directory
3.     mkdir	mkdir graphics	Make a directory called graphics
4.     rmdir	rmdir emptydir	Remove directory (must be empty)
5.     cp	cp file1 web-docs cp file1 file1.bak	Copy file into directory Make backup of file1
6.     rm	rm file1.bak rm *.tmp	Remove or delete file Remove all file
7.     mv	mv old.html new.html	Move or rename files
8.     more	more index.html	Look at file, one page at a time
9.     lpr	lpr index.html	Send file to printer
10.   man	man ls	Online manual (help) about command

Ten VALUABLE UNIX Commands

Once you have mastered the basic UNIX commands, these will be quite valuable in managing your own account.

Command	Example	Description
1.     grep <str><files>	grep "bad word" *	Find which files contain a certain word
2.     chmod <opt> <file>	chmod 644 *.html chmod 755 file.exe	Change file permissions read only Change file permissions to executable
3.     passwd	passwd	Change passwd
4.     ps <opt>	ps aux ps aux   |   grep dhyatt	List all running processes by #ID List process #ID's running by dhyatt
5.     kill <opt> <ID>	kill -9 8453	Kill process with ID #8453
6.     gcc (g++) <source>	gcc file.c -o file g++ fil2.cpp -o fil2	Compile a program written in C Compile a program written in C++
7.     gzip <file>	gzip bigfile gunzip bigfile.gz	Compress file Uncompress file
8.     mail         (pine)	mail me@tjhsst.edu < file1 pine	Send file1 by email to someone Read mail using pine
9.     telnet <host>         ssh <host>	telnet vortex.tjhsst.edu ssh -l dhyatt jazz.tjhsst.edu	Open a connection to vortex Open a secure connection to jazz as user dhyatt
10.   ftp <host> ncftp <host/directory>	ftp station1.tjhsst.edu ncftp metalab.unc.edu	Upload or Download files to station1 Connect to archives at UNC

Ten FUN UNIX Commands

These are ten commands that you might find interesting or amusing. They are actually quite helpful at times, and should not be considered idle entertainment.

Command	Example	Description
1.     who	who	Lists who is logged on your machine
2.     finger	finger	Lists who is on computers in the lab
3.     ytalk <user@place>	ytalk dhyatt@threat	Talk online with dhyatt who is on threat
4.     history	history	Lists commands you've done recently
5.     fortune	fortune	Print random humerous message
6.     date	date	Print out current date
7.     cal <mo> <yr>	cal 9 2000	Print calendar for September 2000
8.     xeyes	xeyes &	Keep track of cursor (in "background")
9.     xcalc	xcalc &	Calculator ("background" process)
10.   mpage <opt> <file>	mpage -8 file1   |  lpr	Print 8 pages on a single sheet and send to printer (the font will be small!)

Ten HELPFUL UNIX Commands

These ten commands are very helpful, especially with graphics and word processing type applications.

Command	Example	Description
1.     netscape	netscape &	Run Netscape browser
2.     xv	xv &	Run graphics file converter
3.     xfig / xpaint	xfig & (xpaint &)	Run drawing program
4.     gimp	gimp &	Run photoshop type program
5.     ispell <fname>	ispell file1	Spell check file1
6.     latex <fname>	latex file.tex	Run LaTeX, a scientific document tool
7.     xemacs / pico	xemacs (or pico)	Different editors
8.     soffice	soffice &	Run StarOffice, a full word processor
9.     m-tools (mdir, mcopy,         mdel, mformat, etc. )	mdir a: mcopy file1   a:	DOS commands from UNIX (dir A:) Copy file1 to A:
10.   gnuplot	gnuplot	Plot data graphically

Ten USEFUL UNIX Commands:

These ten commands are useful for monitoring system access, or simplifying your own environment.

Command	Example	Description
1.     df	df	See how much free disk space
2.     du	du -b subdir	Estimate disk usage of directory in Bytes
3.     alias	alias lls="ls -alF"	Create new command "lls" for long format of ls
4.     xhost	xhost + threat.tjhsst.edu xhost -	Permit window to display from x-window program from threat Allow no x-window access from other systems
5.     fold	fold -s file1   |   lpr	Fold or break long lines at 60 characters and send to printer
6.     tar	tar -cf subdir.tar subdir tar -xvf subdir.tar	Create an archive called subdir.tar of a directory Extract files from an archive file
7.     ghostview (gv)	gv filename.ps	View a Postscript file
8.     ping    (traceroute)	ping threat.tjhsst.edu traceroute www.yahoo.com	See if machine is alive Print data path to a machine
9.     top	top	Print system usage and top resource hogs
10.   logout (exit)	logout or exit	How to quit a UNIX shell.

Some Other Useful Pages

• Some Useful Files and UNIX Commands: pipe, fork, system(), etc.
• Getting Started with vi
• The Basics of HTML
• Making a Web Page
• Using LaTeX
• Generating Graphs with GNU Plot

 

How to check running process (ps -ef command):

Example Uses Of The Linux ps Command

ps command produces a list of the currently running processes on your computer. The ps command is commonly used in conjunction with the grep command and the more or less commands; these additional commands help to filter and paginate the output from ps which can often be quite long. 

 

How to Use the 'ps' Command

On its own, the ps command shows the running processes by the user running it within a terminal window. To invoke ps simply type the following:

ps

The output will show rows of data containing the following information:

• PID
• TTY
• Time
• Command

The PID is the process ID which identifies the running process. The TTY is the terminal type. 

On its own, the ps command is quite limited. You probably want to see all the running processes. To view all the running processes use either of the following commands:

ps -A 

ps -e

To show all of the processes except for session leaders run the following command:

ps -d

So what is a session leader? When one process kicks off other processes it is the session leader of all the other processes. So imagine process A kicks off process B and process C. Process B kicks off process D and process C kicks off process E. When you list all processes except sessions leaders you will see B, C, D, and E but not A.

Negate any of the selections that you have chosen by using the -N switch. For example, to see just the session leaders run the following command:

ps -d -N

The -N is not helpful when used with the -e or -A switches as it will show nothing at all.

To see only the processes associated with this terminal run the following command:

ps T

If you want to see all the running processes using the following command:

ps r

Selecting Specific Processes Using the ps Command

Return specific processes using the ps command and there are various ways to change the selection criteria.

For instance, if you know the process id you can simply use the following command:

ps -p <pid>

You can select multiple processes by specifying multiple process IDs as follows:

ps -p "1234 9778"

You can also specify them using a comma-separated list:

ps -p 1234,9778

The chances are that you won't know the process ID and it is easier to search by command. To do this use the following command:

ps -C <command>

For example, to see if Chrome is running you can use the following command:

ps -C chrome

Other ways to filter results is by group. Search by group name using the following syntax:

ps -G <groupname> ps --Group <groupname>

For example to find out all the processes being run by the accounts group, type the following:

ps -G "accounts" ps --Group "accounts"

You can also search by group id instead of group name by using a lowercase "g" as follows:

ps -g <groupid> ps --group <groupid>

To search by a list of session IDs use the following command:

ps -s <sessionid>

Alternatively, use the following to search by terminal type.

ps -t <sessionid>

To find all the processes run by a specific user try out the following command:

ps U <userlist>

For example, to find all the processes ran by gary run the following:

ps U "gary"

This output shows the person whose credentials are used to run the command. For example, if you are logged in as gary and run the above command it will show all the commands you've executed.

If you log in as Tom and use sudo to run a command then the above command will show Tom's command as being run by gary and not Tom.

To limit the list to just the processes really run by gary use the following command:

ps -U "gary"

Formatting ps Command Output

By default you get the same four columns when you use the ps command:

• PID
• TTY
• Time
• Command

You can get a full listing by running the following command:

ps -ef

The -e, as you know, shows all the processes and the f or -f shows full details.

The columns returned are as follows:

• User ID
• PID
• PPID
• C
• STime
• TTY
• Time
• Command

The User ID is the person who ran the command. The PID is the process ID of the command. The PPID is the parent process that kicked off the command.

The C column shows the number of children a process has. The STime is the start time for the process. The TTY is the terminal, the time is the amount of time it took to run and command is the command that was run.

You can get even more columns by using the following command:

ps -eF

This returns the following columns:

• UID
• PID
• PPID
• C
• SZ
• RSS
• PSR
• STime
• TTY
• Time
• Command

The extra columns are SZ, RSS, and PSR. SZ is the size of the process, RSS is the real memory size and PSR is the processor the command is assigned to.

Specify a user-defined format using the following switch:

ps -e --format <format>

The formats available are as follows:

• %cpu: CPU utilisation
• %mem: Memory percentage utilization
• args: The command with all its arguments
• c: Processor utilization
• cmd: The command
• comm: The command name only
• cp: CPU Usage
• cputime: CPU Time
• egid: Effective group id
• egroup: Effective group
• etime: Elapsed time
• euid: Effective user id
• euser: Effective user
• gid: Group id
• group: Group name
• pgid: Process group id
• pgrp: Process group
• ppid: Parent Process ID
• start: Time the process started
• sz: Size in physical pages
• thcount: Threads owned by the process
• time: Cumulative time
• uid: User Id
• uname: Username

There are many more options but these are the most commonly used ones.

To use the formats type the following:

 ps -e --format="uid uname cmd time"

Mix and match the items as you wish them to be.

Sorting Output

To sort the output, use the following notation:

ps -ef --sort <sortcolumns>

The choice of sort options are as follows:

• cmd: Executable name
• pcpu: CPU utilization
• flags: Flags
• pgrp: Process group id
• cutime: Cumulative user time
• cstime: Cumulative system time
• utime: User time
• pid: Process ID
• ppid: Parent process ID
• size: Size
• uid: User ID
• user: User Name

Again there are more options available but these are the most common ones.

An example sort command is as follows:

ps -ef --sort user,pid

Using 'ps' with 'grep', 'less', and 'more' Commands

It's common to use ps with the grep, less and more commands.

The less and more commands help you sift through the results one page at a time. To use these commands simply pipe the output from grep into them as follows:

ps -ef | more ps -ef | less

The grep command helps you filter the results from the ps command.

For example:

ps -ef | grep chrome 

Summary

The ps command is commonly used for listing processes within Linux. You can also use the top command to display running processes in a different manner.