Basic Linux Commands

Here is basic Linux command introduction. In the examples below, the commands themselves are highlighted in yellow and are followed by the output they produce. Select a topic for details.

1. ls : list files in a directory
2. pwd : show full path to current directory
3. mkdir : make directories
4. cd : change directory
5. cp : copy files and directories
6. rm : remove files
7. rm -rf : remove a directory and everything in it
8. man : show usage manual for a command
9. * ? and other wildcards
10. ~ : shortcut to your home directory
11. ls : list files in a directory

[abc123@testetl]$ ls
Display extra details (file size, type, date, permissions) with the “long” (-l) option:

[abc123@testetl]$ ls -l
total 12
-rw——-     1 abc123 users           1121 Oct 30 16:15 figure1.fig
-rw——-     1 abc123 users             69 Oct 30 16:15 test.m
-rwx——     1 abc123 users             40 Oct 30 16:10 test.sh

You can use wildcards to select only some of the files.

[abc123@testetl]$ ls -l test*
-rw——-     1 abc123 users             69 Oct 30 16:15 test.m
-rwx——     1 abc123 users             40 Oct 30 16:10 test.sh

pwd : show full path to current directory
Print working directory path:

[abc123@testetl]$ pwd
/sscc/home/a/abc123

mkdir : make directories
Create a new subdirectory called subdir in the current directory:

[abc123@testetl]$ mkdir subdir
[abc123@testetl]$ ls -l
total 16
-rw——-     1 abc123 users           1121 Oct 30 16:15 figure1.fig
drwx——     2 abc123 users           4096 Nov 4 13:55 subdir
-rw——-     1 abc123 users             69 Oct 30 16:15 test.m
-rwx——     1 abc123 users             40 Oct 30 16:10 test.sh

cd : change directory
Switch to a subdirectory called subdir in your current directory:

[abc123@testetl]$ cd subdir
[abc123@seldon subdir]$

Two dots .. denote one directory up in your path:

[abc123@seldon subdir]$ cd ..
[abc123@testetl]$

To use the full path start with a slash:

[abc123@testetl]$ cd /datalib/cps
[abc123@seldon cps]$ pwd/datalib/cps

cp : copy files and directories
Syntax:

cp [options]… Source Destination
cp [options]… Source… Directory

Options:

-i : prompt before overwriting files
-r : copy recursively (copy subdirectories and their contents)
-u : overwrite destination files only when the source file is newer
-v : show what is being done
Make a copy of a file called make.do with a different name:

[abc123@testetl]$ cp -v make.do make2.do
`make.do’ -> `make2.do’

Copy one or more files to another directory:

[abc123@testetl]$ cp -v *.do subdir/
`make.do’ -> `subdir/make.do’
`make2.do’ -> `subdir/make2.do’

Copy the contents of a directory and its subdirectories to another place:

[abc123@testetl]$ cp -vR subdir/* subdir2/
`subdir/make.do’ -> `subdir2/make.do’
`subdir/make2.do’ -> `subdir2/make2.do’
`subdir/data/file.dat’ -> `subdir2/data/file.dat’

rm : remove files
Remove a file called make.do:

[abc123@testetl]$ rm make.do

To remove a file with spaces in its name, use quotes:

[abc123@testetl]$ rm “file name.txt”

To remove multiple files (or to save time typing long file names) use wildcards. Be careful – wildcards are powerful and could match more files than you intended. Use the ls command first to check what files will be deleted.

[abc123@testetl]$ rm *.txt

rm -rf : remove a directory and everything in it
Delete a subdirectory called subdir and all of its contents (including its subdirectories).

[abc123@testetl]$ rm -rf subdir

man : show usage manual for a command
Display a more detailed manual for a command:

Press <Space bar> to view the next page
Press q to exit
[ate533@seldon ate533]$ man cp
CP(1)                                 FSF
CP(1)

NAME
cp – copy files and directories

SYNOPSIS
cp [OPTION]… SOURCE DEST
cp [OPTION]… SOURCE… DIRECTORY
cp [OPTION]… –target-directory=DIRECTORY SOURCE…

DESCRIPTION
Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
. . .

* ? and other wildcards
You can use these powerful wildcards with any command that takes filenames as an argument. For example prog??.* will match all files with names that start with prog followed by any two characters, a dot, and anything (or nothing) following the dot.

Wildcard Matches
* zero or more characters
? exactly one character
[abxy] exactly one character from the list (a, b, x or y)
[a-e] exactly one character in the given range (a, b, c, d or e)
[!abxy] any character that is not listed
[!a-e] any character that is not in the given range
{beef,fish,tofu} exactly one entire word from the list in curly brackets (beef, fish or tofu)

~ : shortcut to your home directory
You can reference your home directory in your commands and programs with the character tilde ~ shortcut. If your home directory is

/sscc/home/a/abc123

then instead of writing out the full path to the file

/sscc/home/a/abc123/data/input.dat

you can just write

~/data/input.dat

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