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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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sort [options] [files]

Sort the lines of the named files. Compare specified fields for each pair of lines; if no fields are specified, compare them by byte, in machine-collating sequence. If no files are specified or if the file is -, the input is taken from standard input. See also uniq, comm, and join.


-b, --ignore-leading-blanks

Ignore leading spaces and tabs.

-c, --check

Check whether files are already sorted and, if so, produce no output.

-d, --dictionary-order

Sort in dictionary order.

-f, --ignore-case

Fold; ignore uppercase/lowercase differences.

-g, --general-numeric-sort

Sort in general numeric order.


Print a help message and then exit.

-i, --ignore-nonprinting

Ignore nonprinting characters (those outside ASCII range 040-176).

-k n[,m] , --key=n[,m]

Skip n-1 fields and stop at m-1 fields (i.e., start sorting at the nth field, where the fields are numbered beginning with 1).


Sort in arithmetic order.

-ofile, --output=file

Put output in file.

-m, --merge

Merge already sorted input files.

-r, --reverse

Reverse the order of the sort.

-s, --stable

Stabilize sort by disabling last-resort comparison.

-tc, --field-separator=c

Separate fields with c (default is a tab).

-u, --unique

Identical lines in input file appear only one time in output.

-z, --zero-terminated

End lines with zero byte, not with newline.


Print version information and then exit.

-M, --month-sort

Attempt to treat the first three characters as a month designation (JAN, FEB, etc.). In comparisons, treat JAN < FEB and any invalid name for a month as less than a valid month.

-Ssize, --buffer-size=size

Set the size of the main memory buffer to size, which may include a suffix—e.g., K (1024, the default) or M.

-T tempdir, --temporary-directory=dir

Directory pathname to be used for temporary files.


List files by decreasing number of lines:

wc -l * | sort -r

Alphabetize a list of words, remove duplicates, and print the frequency of each word:

sort -fd wordlist | uniq -c

Sort the password file numerically by the third field (user ID):

sort -nk3,4 -t: /etc/passwd

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