ls in unix / linux

1. Use ls without any arguments to display your current directory contents. How many files do you see?
2. Now use ls with the -a option. How many files do you see this time? Notice that the "new" files all begin with a "dot", which indicates they are "hidden" files.

   
        ls -a
        

3. This command is useful for distinguishing between directories, ordinary files, and executable files. Notice how its output differs from ls without arguments.

   
        ls -F
        

4. Use the command ls -l to obtain a "long" listing of your files. Sample output from this command and an explanation of the information it provides appears below.

   
   -rwxr-xr-x   1 jsmith   staff         43 Mar 23 18:14 prog1
   -rw-r--r--   1 jsmith   staff      10030 Mar 22 20:41 sample.f
   drwxr-sr-x   2 jsmith   staff        512 Mar 23 18:07 subdir1
   drwxr-sr-x   2 jsmith   staff        512 Mar 23 18:06 subdir2
   drwxr-sr-x   2 jsmith   staff        512 Mar 23 18:06 subdir3
       1        2   3        4           5       6          7
   
   1 = access modes/permissions
   2 = number of links
   3 = owner
   4 = group
   5 = size (in bytes)
   6 = date/time of last modification
   7 = name of file  
        

5. Recursive listings can be very useful. Try both of the commands below. What does the output tell you?

   
        ls -R
        ls -Rl
        

6. Try three options together:

   
        ls -lFa
        

More options

-a, --all

do not hide entries starting with .

-A, --almost-all

do not list implied . and ..

--author

print the author of each file

-b, --escape

print octal escapes for nongraphic characters

--block-size=SIZE

use SIZE-byte blocks

-B, --ignore-backups

do not list implied entries ending with ~

-c

with -lt: sort by, and show, ctime (time of last modification of file status information) with -l: show ctime and sort by name otherwise: sort by ctime

-C

list entries by columns

--color[=WHEN]

control whether color is used to distinguish file types. WHEN may be `never', `always', or `auto'

-d, --directory

list directory entries instead of contents

-D, --dired

generate output designed for Emacs' dired mode

-f

do not sort, enable -aU, disable -lst

-F, --classify

append indicator (one of */=@|) to entries

--format=WORD

across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C

--full-time

like -l --time-style=full-iso

-g

like -l, but do not list owner

-G, --no-group

inhibit display of group information

-h, --human-readable

print sizes in human readable format (e.g., 1K 234M 2G)

--si

likewise, but use powers of 1000 not 1024

-H, --dereference-command-line

follow symbolic links on the command line

--indicator-style=WORD append indicator with style WORD to entry names:

none (default), classify (-F), file-type (-p)

-i, --inode

print index number of each file

-I, --ignore=PATTERN

do not list implied entries matching shell PATTERN

-k

like --block-size=1K

-l

use a long listing format (shows permission , owner, size and last modified)

-L, --dereference

when showing file information for a symbolic link, show information for the file the link references rather than for the link itself

-m

fill width with a comma separated list of entries

-n, --numeric-uid-gid

like -l, but list numeric UIDs and GIDs

-N, --literal

print raw entry names (don't treat e.g. control characters specially)

-o

like -l, but do not list group information

-p, --file-type

append indicator (one of /=@|) to entries

-q, --hide-control-chars

print ? instead of non graphic characters

--show-control-chars

show non graphic characters as-is (default unless program is `ls' and output is a terminal)

-Q, --quote-name

enclose entry names in double quotes

--quoting-style=WORD

use quoting style WORD for entry names: literal, locale, shell, shell-always, c, escape

-r, --reverse

reverse order while sorting

-R, --recursive

list subdirectories recursively

-s, --size

print size of each file, in blocks

-S

sort by file size

--sort=WORD

extension -X, none -U, size -S, time -t, version -v

status -c, time -t, atime -u, access -u, use -u

--time=WORD

show time as WORD instead of modification time: atime, access, use, ctime or status; use specified time as sort key if --sort=time

--time-style=STYLE

show times using style STYLE: full-iso, long-iso, iso, locale, +FORMAT

FORMAT is interpreted like `date'; if FORMAT is FORMAT1FORMAT2, FORMAT1 applies to non-recent files and FORMAT2 to recent files; if STYLE is prefixed with `posix-', STYLE takes effect only outside the POSIX locale

-t

sort by modification time

-T, --tabsize=COLS

assume tab stops at each COLS instead of 8

-u

with -lt: sort by, and show, access time with -l: show access time and sort by name otherwise: sort by access time

-U

do not sort; list entries in directory order

-v

sort by version

-w, --width=COLS

assume screen width instead of current value

-x

list entries by lines instead of by columns

-X

sort alphabetically by entry extension

-1

list one file per line

--help

display this help and exit

--version

output version information and exit