Unix / Linux – Shell Manpage Help

Unix / Linux - Shell Manpage Help - myTechMint
All the Unix commands come with a number of optional and mandatory options. It is very common to forget the complete syntax of these commands.
Because no one can possibly remember every Unix command and all its options, we have online help available to mitigate this right from when Unix was at its development stage.
Unix’s version of Help files are called man pages. If there is a command name and you are not sure how to use it, then Man Pages help you out with every step.

Syntax

Here is the simple command that helps you get the detail of any Unix command while working with the system −
$man command

Example

Suppose there is a command that requires you to get help; assume that you want to know about pwd then you simply need to use the following command −
$man pwd
The above command helps you with the complete information about the pwd command. Try it yourself at your command prompt to get more detail.
You can get complete detail on man command itself using the following command −
$man man

Man Page Sections

Man pages are generally divided into sections, which generally vary by the man page author’s preference. Following table lists some common sections −
Sr.No. Section & Description
1
NAME
Name of the command
2
SYNOPSIS
General usage parameters of the command
3
DESCRIPTION
Describes what the command does
4
OPTIONS
Describes all the arguments or options to the command
5
SEE ALSO
Lists other commands that are directly related to the command in the man page or closely resemble its functionality
6
BUGS
Explains any known issues or bugs that exist with the command or its output
7
EXAMPLES
Common usage examples that give the reader an idea of how the command can be used
8
AUTHORS
The author of the man page/command
To sum it up, man pages are a vital resource and the first avenue of research when you need information about commands or files in a Unix system.

Useful Shell Commands

The following link gives you a list of the most important and very frequently used Unix Shell commands.
If you do not know how to use any command, then use man page to get complete detail about the command.
Here is the list of Unix Shell – Useful Commands
This quick guide lists commands, including a syntax and a brief description. For more detail, use −
$man command

Files and Directories

These commands allow you to create directories and handle files.

Sr.No. Command & Description
1
cat
Displays File Contents
2
cd
Changes Directory to dirname
3
chgrp
Changes file group
4
chmod
Changes permissions
5
cp
Copies source file into destination
6
file
Determines file type
7
find
Finds files
8
grep
Searches files for regular expressions
9
head
Displays first few lines of a file
10
ln
Creates softlink on oldname
11
ls
Displays information about file type
12
mkdir
Creates a new directory dirname
13
more
Displays data in paginated form
14
mv
Moves (Renames) an oldname to newname
15
pwd
Prints current working directory
16
rm
Removes (Deletes) filename
17
rmdir
Deletes an existing directory provided it is empty
18
tail
Prints last few lines in a file
19
touch
Updates access and modification time of a file

Manipulating data

The contents of files can be compared and altered with the following commands.

Sr.No. Command & Description
1
awk
Pattern scanning and processing language
2
cmp
Compares the contents of two files
3
comm
Compares sorted data
4
cut
Cuts out selected fields of each line of a file
5
diff
Differential file comparator
6
expand
Expands tabs to spaces
7
join
Joins files on some common field
8
perl
Data manipulation language
9
sed
Stream text editor
10
sort
Sorts file data
11
split
Splits file into smaller files
12
tr
Translates characters
13
uniq
Reports repeated lines in a file
14
wc
Counts words, lines, and characters
15
vi
Opens vi text editor
16
vim
Opens vim text editor
17
fmt
Simple text formatter
18
spell
Checks text for spelling error
19
ispell
Checks text for spelling error
20
emacs
GNU project Emacs
21
ex, edit
Line editor
22
emacs
GNU project Emacs

Compressed Files

Files may be compressed to save space. Compressed files can be created and examined.
Sr.No. Command & Description
1
compress
Compresses files
2
gunzip
Helps uncompress gzipped files
3
gzip
GNU alternative compression method
4
uncompress
Helps uncompress files
5
unzip
List, test and extract compressed files in a ZIP archive
6
zcat
Cat a compressed file
7
zcmp
Compares compressed files
8
zdiff
Compares compressed files
9
zmore
File perusal filter for crt viewing of compressed text

Getting Information

Various Unix manuals and documentation are available on-line. The following Shell commands give information −
Sr.No. Command & Description
1
apropos
Locates commands by keyword lookup
2
info
Displays command information pages online
2
man
Displays manual pages online
3
whatis
Searches the whatis database for complete words
4
yelp
GNOME help viewer

Network Communication

These following commands are used to send and receive files from a local Unix hosts to the remote host around the world.
Sr.No. Command & Description
1
ftp
File transfer program
2
rcp
Remote file copy
3
rlogin
Remote login to a Unix host
4
rsh
Remote shell
5
tftp
Trivial file transfer program
6
telnet
Makes terminal connection to another host
7
ssh
Secures shell terminal or command connection
8
scp
Secures shell remote file copy
9
sftp
Secures shell file transfer program
Some of these commands may be restricted at your computer for security reasons.

Messages between Users

The Unix systems support on-screen messages to other users and world-wide electronic mail −
Sr.No. Command & Description
1
evolution
GUI mail handling tool on Linux
2
mail
Simple send or read mail program
3
mesg
Permits or denies messages
4
parcel
Sends files to another user
5
pine
Vdu-based mail utility
6
talk
Talks to another user
7
write
Writes message to another user

Programming Utilities

The following programming tools and languages are available based on what you have installed on your Unix.

Sr.No. Command & Description
1
dbx
Sun debugger
2
gdb
GNU debugger
3
make
Maintains program groups and compile programs
4
nm
Prints program’s name list
5
size
Prints program’s sizes
6
strip
Removes symbol table and relocation bits
7
cb
C program beautifier
8
cc
ANSI C compiler for Suns SPARC systems
9
ctrace
C program debugger
10
gcc
GNU ANSI C Compiler
11
indent
Indent and format C program source
12
bc
Interactive arithmetic language processor
13
gcl
GNU Common Lisp
14
perl
General purpose language
15
php
Web page embedded language
16
py
Python language interpreter
17
asp
Web page embedded language
18
CC
C++ compiler for Suns SPARC systems
19
g++
GNU C++ Compiler
20
javac
JAVA compiler
21
appletvieweir
JAVA applet viewer
22
netbeans
Java integrated development environment on Linux
23
sqlplus
Runs the Oracle SQL interpreter
24
sqlldr
Runs the Oracle SQL data loader
25
mysql
Runs the mysql SQL interpreter

Misc Commands

These commands list or alter information about the system −

Sr.No. Command & Description
1
chfn
Changes your finger information
2
chgrp
Changes the group ownership of a file
3
chown
Changes owner
4
date
Prints the date
5
determin
Automatically finds terminal type
6
du
Prints amount of disk usage
7
echo
Echo arguments to the standard options
8
exit
Quits the system
9
finger
Prints information about logged-in users
10
groupadd
Creates a user group
11
groups
Show group memberships
12
homequota
Shows quota and file usage
13
iostat
Reports I/O statistics
14
kill
Sends a signal to a process
15
last
Shows last logins of users
16
logout
Logs off Unix
17
lun
Lists user names or login ID
18
netstat
Shows network status
19
passwd
Changes user password
20
passwd
Changes your login password
21
printenv
Displays value of a shell variable
22
ps
Displays the status of current processes
23
ps
Prints process status statistics
24
quota -v
Displays disk usage and limits
25
reset
Resets terminal mode
26
script
Keeps script of terminal session
27
script
Saves the output of a command or process
28
setenv
Sets environment variables
30
stty
Sets terminal options
31
time
Helps time a command
32
top
Displays all system processes
33
tset
Sets terminal mode
34
tty
Prints current terminal name
35
umask
Show the permissions that are given to view files by default
36
uname
Displays name of the current system
37
uptime
Gets the system up time
38
useradd
Creates a user account
39
users
Prints names of logged in users
40
vmstat
Reports virtual memory statistics
41
w
Shows what logged in users are doing
42
who
Lists logged in users

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