NAME

sort — sort lines of text

SYNOPSIS

DESCRIPTION

sort reads lines of text from the standard input and writes the lines in sorted order to the standard output. If files are specified, the input is the concatenated content of the files read in sequential order. The file path can be set to ‘-’ to specify the standard input. The lines are compared according to the current locale's collating rules.

The options are as follows:

-c, --check, --check=diagnose-first

Check whether the input is already sorted. If a line is out of order (or an equal line is found if -u), write an error describing which line was out of order and exit 1.

-C, --check=quiet, --check=silent

Same as -c, but write no error to the standard output about the input being out of order.

-m, --merge

Merge the presorted input files into a sorted output.

-o path, --output=path

After reading the full input; write the output to the file at path (creating it if it does not already exist, discarding its previous contents if it already existed). The output file can be one of the input files. This option is incompatible with -C and -c.

-R, --random-sort

Sort the lines randomly with a uniform distribution, where all permutations are equally likely. This option is incompatible with -C and -c. If -u, don't write duplicate lines to the output.

-r, --reverse

Compare the lines in reverse order.

-u, --unique

Don't write a line if it is equal to the previous line.

-V, --version-sort

Sort according to the version string, per strverscmp(3).

-z, --zero-terminated

Lines are delimited with the NUL byte (0) instead of the newline byte (10).

IMPLEMENTATION NOTES

In the event of an input error, sort will write an error to the standard error and exit unsuccessfully.

sort reads the whole input into memory, rather than storing intermediate sorting steps in the filesystem, and requires enough memory to store a copy of the whole input.

ENVIRONMENT

LANG

The default locale for locale variables that are unset or null.

LC_ALL

Overrides all the other locale variables if set.

LC_COLLATE

Compare the input according to this locale's collating rules using strcoll(3).

EXIT STATUS

sort will exit 0 on success, exit 1 if the input was out of order when -C or -c, or exit 2 (or higher) otherwise.

EXAMPLES

Read lines from the standard input and write them in sorted order to the standard output:

sort < input > output

Read lines from the three specified files (where the second happens to be the standard input) and write them in sorted to the standard output:

grep pattern lines.txt | sort foo - bar -o output.txt

Sort the input file if it isn't already sorted:

if sort -C file; [ $? = 1 ]; then
  sort file -o file
fi

Remove duplicate lines from the input by sorting it and removing lines equal to the previous line:

sort -u

SEE ALSO

cat(1), comm(1), join(1), uniq(1), qsort(3), strcoll(3), strverscmp(3)

STANDARDS

sort is standardized in IEEE Std 1003.1-2008 (“POSIX.1”), which is currently partially implemented in this implementation of sort.

The -R, -V, and -z options, as well as the long options, are extensions also found in GNU coreutils.

Unlike GNU coreutils, -R will not remove duplicates unless -u is passed.

As an extension, the -C and -c options support multiple input files.

BUGS

The IEEE Std 1003.1-2008 (“POSIX.1”) options -b, -d, -f, -i, -k, -n, and -t are not currently implemented.

The -m option is not currently taken advantage of to speed up the sorting, rather the presorted input files are sorted all over again.