ls

ls

ls command is used to list the contents off the directory.ls writes to standard output

all  the information of the files, directories or specifically  of the parameters passed to it.

You can display these contents in the alphabetically sorted order, or list only particular  files  in

Combination with other command. There are many options with ls which you  may hardly use in normal cases.

Here ,only few frequently used options are discussed.

Example 1)

To simply display the names of all the files in a directory.

/home/script-user$ ls

Joke-and-fun.xt

Send_script.sh

Mail-file

Rollercoaster

Jackson_note.tar

Example  2)

To display all the files that  have a common  pattern.

/home/script-user/items $ ls table_*.log

table_111.log

table_x.log

table_te1.log

table_adam.log

Example 3)

 To  get a long listing of files which contains all the details such as file size, permissions,

Time stamp, user details sorted by the modification time, use ls as follows.

/home/script-user $ ls  –lrt   

-rw-r--r--    1  script-user  Tools    56344   Dec 16     14:37 Joke-and-fun.xt

-rw-r--r--    1  script-user  Tools   105977 Dec 16     15:52  Send_script.sh

 drw-r--r--  2  script-user  Tools      256      Dec 18      21:01 Mail-file

-rw-r--r--    1  script-user  Tools      740      Dec 20      01:03 Rollercoaster

-rw-r--r--    1  script-user  Tools       58        Dec 24     00:40 Jackson_note.tar

The first field here shows file permissions, which are discussed in chmod,

2^nd field is the type of element,(1 for file 2 for directory..etc)

3^rd field gives the owner of the element(file,directory)

4^th field gives the group which the user belongs to.

5^th field gives the size.

6^th,7^th and 8^th field-modification times.

9 th field gives the name of the element.

You can get any field of the output of ls –lrt using awk.

For eg: To  get the name of the element from the output of ls –lrt, use awk as follows

/home/script-user $ ls  -lrt  |  awk  ‘{print  $9}’

Joke-and-fun.xt

Send_script.sh

 Mail-file

Rollercoaster

Jackson_note.tar

Example 4)

To display only the directories in a path, use the output of  ls –lrt  as follows.

/home/script-user $ ls  -lrt  |  grep “^d”

 drw-r--r--  2  script-user  Tools       256      Dec 18      21:01 Mail-file

The  ‘^’  character represents  a starting character of a line( a ‘$’ represents end), in fact  it’s not physically seen, but an  interpreted character.

In  this case grep searched for the  lines starting with  a  ‘d’ which stands for directories.

Example 5)

 you want to list the directories whose name has a common pattern, use ls  –ld  <pattern>

home/script-user/ebooks $ls   -ld  j*

drwxr-xr-x    2 script-user  Tools        256      Nov  9 12:10  j2me

drwxr-xr-x    2 script-user  Tools    20480     Nov  9 12:10  java

drwxr-xr-x    2 script-user  Tools     4096      Nov  9 12:10  java scripts

Suppose you want to view all the files of the directory  java  use  ls –lrt  java instead of doing  both cd java and ls –lrt.

Example  6)

To  make  a case insensitive list on a filename parameter, use ls along with grep as follows.

home/script-user/docs$ ls   report*

report1.doc

report_eng.doc

reportslist.txt

home/script-user/docs$ls  |  grep  –i   report

 report1.doc

report_eng.doc

reportslist.txt

Reports_Bulk.wrt

Business_reports.doc

The above command is equivalent to  ls  *report*  *Report*   *REPORT*  *Report*………..and so on till all the combination of the word report in Ucase and Lcase.

Example 7)

To  list all the directories in a directory, and its subdirectories, use ls –R

In this case ls lists all the files inside the directories  starting with j recursively in all its subdirectories.

home/script-user/ebooks $ ls  -R  j*

j2me:

j2me - the complete reference.pdf  j2me---the-complete-reference.htm

java:<----------------------------     directory

 java The J2EE Tutorial (Addison Wesley & Sun, 2002).pdf

(Addison Wesley 2002) - Java Network Programming and Distributed Computing.pdf

(Ebook) Java - Borland Jbuilder - Developing Database Applications - Inprise.pdf

(OReilly) Java Network Programming ,2nd Ed.pdf

(OReilly) Java Server Pages ,2nd Ed.pdf

java scripts:

[Java Script] O'Reilly- JavaScript The Definitive Guide.pdf

java scripts/newdir:<-------------  subdirectory

[Java Script] O'Reilly - JavaScript The Definitive Guide 2ed.pdf

….

….

…

^C

Example  8)

ls  by default does not show hidden files and directories. To show hidden files use –a option.

Eg: files like  .profile, .sh_history etc are hidden files. if  have not used –a option you wont be

 able to see these files.

In all the directories , there are 2 common hidden directories  .(a dot)  which represents the current directory and  ..( 2 dots) represents the parent of the current directory