Listing Files

The ls command is used to list the contents of a directory. You've already seen it used a few times before in examples, but this page will help ensure you are comfortable with its use.

ls [OPTIONS] [FILE]

By default, when the ls command is used with no options or arguments, it will list the files in the current directory:

sysadmin@localhost:~$ ls
Desktop  Documents  Downloads  Music  Pictures  Public  Templates  Videos

To learn the details about a file, such as the type of file, the permissions, ownerships or the timestamp, perform a long listing using the -l option to the ls command. Below, a listing of the /var/log directory is used as an example, since it provides a variety of output: ⁠‌‌⁠⁠⁠⁠

sysadmin@localhost:~$ ls -l /var/log/
total 832
-rw-r--r-- 1 root   root  17869 Mar 14 17:48 alternatives.log
drwxr-x--- 2 root   adm    4096 Mar 14 17:48 apache2
drwxr-xr-x 2 root   root   4096 Mar 14 17:45 apt
-rw-r----- 1 syslog adm     380 Jul 28 03:45 auth.log
-rw-r--r-- 5 root   root  47816 Mar  2 23:10 bootstrap.log
-rw-rw---- 5 root   utmp      0 Mar  2 23:10 btmp
-rw-r----- 1 syslog adm     324 Jul 28 03:45 cron.log
-rw-r----- 1 root   adm   85083 Mar 14 17:48 dmesg
-rw-r--r-- 1 root   root 315196 Mar 14 17:48 dpkg.log
-rw-r--r-- 1 root   root  32064 Mar 14 17:48 faillog
drwxr-xr-x 2 root   root   4096 Jun 30 06:53 fsck
-rw-r----- 1 syslog adm     106 Jul 28 03:45 kern.log
-rw-rw-r-- 1 root   utmp 292584 Jul 28 03:45 lastlog
-rw-r----- 1 syslog adm   18703 Jul 28 03:46 syslog
drwxr-xr-x 2 root   root   4096 Apr 11  2014 upstart
-rw-rw-r-- 1 root   utmp    384 Jul 28 03:45 wtmp

Each line corresponds to a file contained within the directory. The information can be broken down into fields separated by spaces. The fields are as follows:

File Type

-rw-r--r-- 1 root   root  17869 Mar 14 17:48 alternatives.log                   
drwxr-x--- 2 root   adm    4096 Mar 14 17:48 apache2

The first field actually contains ten characters, where the first character indicates the type of file and the next nine specify permissions. The file types are:

Symbol	File Type	Description
`d`	directory	A file used to store other files.
`-`	regular file	Includes readable files, images files, binary files, and compressed files.
`l`	symbolic link	Points to another file.
`s`	socket	Allows for communication between processes.
`p`	pipe	Allows for communication between processes.
`b`	block file	Used to communicate with hardware.
`c`	character file	Used to communicate with hardware.

The first file alternatives.log is a regular file -, while the second file apache2 is a directory d.

Permissions

drwxr-xr-x 1 root root 0 Apr 11 21:58 upstart

Permissions indicate how certain users can access a file. Keep reading to learn more about permissions.

Hard Link Count
```
-rw-r----- 1 syslog adm 23621 Aug 23 15:17 auth.log
```
This number indicates how many hard links point to this file. Hard links are beyond the scope of this module, but are covered in the NDG Linux Essentials course.
User Owner
```
-rw-r----- 1 syslog adm 416 Aug 22 15:43 kern.log
```
User syslog owns this file. Every time a file is created, the ownership is automatically assigned to the user who created it.

Group Owner

-rw-rw-r-- 1 root utmp 292584 Aug 20 18:44 lastlog

Indicates which group owns this file

File Size
```
-rw-r----- 1 syslog adm 1087150 Aug 23 15:17 syslog.1
```
The size of the file in bytes. In the case of a directory, it might actually be a multiple of the block size used for the file system.
Timestamp
```
drwxr-xr-x 1 root root 32 Jul 17 03:36 fsck
```
This indicates the time that the file's contents were last modified.
Filename
```
-rw-r--r-- 1 root root 47816 Jul 17 03:36 bootstrap.log
```
The final field contains the name of the file or directory.
Remember This

In the case of symbolic links, the link name will be displayed along with an arrow and the pathname of the original file.
```
lrwxrwxrwx. 1 root root 22 Nov 6 2012 /etc/grub.conf -> ../boot/grub/grub.conf
```
Symbolic links are beyond the scope of this module, but are covered in greater detail in the NDG Linux Essentials course.

Sorting

By default the output of the ls command is sorted alphabetically by filename. It can sort by other methods as well.

Follow Along

The options in examples below will be combined with the -l option so the relevant details of the files are displayed. Notice fields corresponding to the search option.

The -t option will sort the files by timestamp:

sysadmin@localhost:~$ ls -lt /var/log                                           
total 840                                                                       
-rw-r----- 1 syslog adm   27014 Jul 28 00:10 syslog                             
-rw-r----- 1 syslog adm     380 Jul 27 23:10 auth.log                           
-rw-rw-r-- 1 root   utmp 292584 Jul 27 23:10 lastlog                            
-rw-rw-r-- 1 root   utmp    384 Jul 27 23:10 wtmp                               
-rw-r----- 1 syslog adm     324 Jul 27 23:10 cron.log                           
-rw-r----- 1 syslog adm     106 Jul 27 23:10 kern.log                           
drwxr-xr-x 2 root   root   4096 Jun 30 06:56 fsck                               
-rw-r--r-- 1 root   root  17869 Mar 14 17:48 alternatives.log                   
-rw-r----- 1 root   adm   85083 Mar 14 17:48 dmesg                              
-rw-r--r-- 1 root   root  32064 Mar 14 17:48 faillog                            
-rw-r--r-- 1 root   root 315196 Mar 14 17:48 dpkg.log                           
drwxr-x--- 2 root   adm    4096 Mar 14 17:48 apache2                            
drwxr-xr-x 2 root   root   4096 Mar 14 17:45 apt                                
-rw-r--r-- 5 root   root  47816 Mar  2 23:10 bootstrap.log                      
-rw-rw---- 5 root   utmp      0 Mar  2 23:10 btmp                               
drwxr-xr-x 2 root   root   4096 Apr 11  2014 upstart

The -S option will sort the files by file size:

sysadmin@localhost:~$ ls -l -S /var/log                                         
total 840                                                                       
-rw-r--r-- 1 root   root 315196 Mar 14 17:48 dpkg.log                           
-rw-rw-r-- 1 root   utmp 292584 Jul 27 23:10 lastlog                            
-rw-r----- 1 root   adm   85083 Mar 14 17:48 dmesg                              
-rw-r--r-- 5 root   root  47816 Mar  2 23:10 bootstrap.log                      
-rw-r--r-- 1 root   root  32064 Mar 14 17:48 faillog                            
-rw-r----- 1 syslog adm   27014 Jul 28 00:10 syslog                             
-rw-r--r-- 1 root   root  17869 Mar 14 17:48 alternatives.log                   
drwxr-x--- 2 root   adm    4096 Mar 14 17:48 apache2                            
drwxr-xr-x 2 root   root   4096 Mar 14 17:45 apt                                
drwxr-xr-x 2 root   root   4096 Jun 30 06:56 fsck                               
drwxr-xr-x 2 root   root   4096 Apr 11  2014 upstart                            
-rw-rw-r-- 1 root   utmp    384 Jul 27 23:10 wtmp                               
-rw-r----- 1 syslog adm     380 Jul 27 23:10 auth.log                           
-rw-r----- 1 syslog adm     324 Jul 27 23:10 cron.log                           
-rw-r----- 1 syslog adm     106 Jul 27 23:10 kern.log                           
-rw-rw---- 5 root   utmp      0 Mar  2 23:10 btmp

The -r option will reverse the order of any type of sort. Notice the difference when it is added to the previous example:

sysadmin@localhost:~$ ls -lSr /var/log
total 840
-rw-rw---- 5 root   utmp      0 Mar  2 23:10 btmp
-rw-r----- 1 syslog adm     106 Jul 27 23:10 kern.log
-rw-r----- 1 syslog adm     324 Jul 27 23:10 cron.log
-rw-r----- 1 syslog adm     380 Jul 27 23:10 auth.log
-rw-rw-r-- 1 root   utmp    384 Jul 27 23:10 wtmp
drwxr-xr-x 2 root   root   4096 Apr 11  2014 upstart
drwxr-xr-x 2 root   root   4096 Jun 30 06:56 fsck
drwxr-xr-x 2 root   root   4096 Mar 14 17:45 apt
drwxr-x--- 2 root   adm    4096 Mar 14 17:48 apache2
-rw-r--r-- 1 root   root  17869 Mar 14 17:48 alternatives.log
-rw-r----- 1 syslog adm   27014 Jul 28 00:10 syslog
-rw-r--r-- 1 root   root  32064 Mar 14 17:48 faillog
-rw-r--r-- 5 root   root  47816 Mar  2 23:10 bootstrap.log
-rw-r----- 1 root   adm   85083 Mar 14 17:48 dmesg
-rw-rw-r-- 1 root   utmp 292584 Jul 27 23:10 lastlog
-rw-r--r-- 1 root   root 315196 Mar 14 17:48 dpkg.log

The numbers in file size field switch from descending to ascending.

Used alone the -r option with list the files in reverse alphabetical order:

sysadmin@localhost:~$ ls -r /var/log                                            
wtmp     lastlog   faillog   cron.log       auth.log  alternatives.log
upstart  kern.log  dpkg.log  btmp           apt
syslog   fsck      dmesg     bootstrap.log

Search This Blog

Listing Files

Sorting

Comments

Post a Comment