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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uniq
uniq [options] [file1 [file2] ]
Remove duplicate adjacent lines from sorted file1 or from standard input, sending one copy of each line to file2 (or to standard output). Often used as a filter. Specify only one of -d or -u. See also comm and sort.
Options
Print each line once, prefixing number of instances.
Print duplicate lines once but no unique lines.
Print all duplicate lines. -D takes no delimiter method. The delimiter method method takes one of the following values: none (default), prepend, or separate. Blank lines are used as the delimiter.
Ignore first n fields of a line. Fields are separated by spaces or by tabs.
Ignore case differences when checking for duplicates.
Ignore first n characters of a field.
Print only unique lines (no copy of duplicate entries is kept).
Compare only first n characters per line (beginning after skipped fields and characters).
Print a help message and then exit.
Print version information and then exit.
Examples
Send one copy of each line from list to output file list.new:
uniq list list.new
Show which names appear more than once:
sort names | uniq -d
