SORT(1)

NAME
sort - sort or merge text files

SYNOPSIS
sort [-cmubdfinr] [-t char] [-R char] [ -k field1[,field2]] ... [-T dir] [-o output] [file] ...

DESCRIPTION
The sort utility sorts text files by lines. Comparisons are based on one or more sort keys extracted from each line of input, and are performed lexicographically. By default, if keys are not given, sort regards each input line as a single field.

The following options are available:

-c  Check that the single input file is sorted. If the file is not sorted, sort produces the appropriate error messages and exits with code 1; otherwise, sort returns 0. Sort -c produces no output.

-m  Merge only; the input files are assumed to be pre-sorted.

-o output
    The argument given is the name of an output file to be used instead of the standard output. This file can be the same as one of the input files.

-T dir
    Use dir as the directory for temporary files. The default is the contents of the environment variable TMPDIR or /var/tmp if TMPDIR does not exist.

-u  Unique: suppress all but one in each set of lines having equal keys. If used with the -c option, check that there are no lines with duplicate keys.

The following options override the default ordering rules. When ordering options appear independent of key field specifications, the requested field ordering rules are applied globally to all sort keys. When attached to a specific key (see -k), the ordering options override all global ordering options for that key.

-d  Only blank space and alphanumeric characters are used in making comparisons.

-f  Considers all lowercase characters that have uppercase equivalents to be the same for purposes of comparison.

-i  Ignore all non-printable characters.

-n  An initial numeric string, consisting of optional blank space, optional minus sign, and zero or more digits (including decimal point) is sorted by arithmetic value. (The -n option no longer implies the -b option.)

-r  Reverse the sense of comparisons.

-H  Use a merge sort instead of a radix sort. This option should be used for files larger than 60Mb.

The treatment of field separators can be altered using the options:

-b  Ignores leading blank space when determining the start and end of a restricted sort key. A -b option specified before the first -k option applies globally to all -k options. Otherwise, the -b option can be attached independently to each field argument of the -k option (see below). Note that the -b option has no effect unless key fields are specified.

-t char
    Char is used as the field separator character. The initial char is not considered to be part of a field when determining key offsets (see below). Each occurrence of char is significant (for example, “charchar” delimits an empty field). If -t is not specified, blank space characters are used as default field separators.

-R char
    Char is used as the record separator character. This should be used with discretion; -R <alphanumeric> usually produces undesirable results. The default line separator is newline.

-k field1[,field2]
    Designates the starting position, field1, and optional ending position, field2, of a key field. The -k option replaces the obsolescent options +pos1 and -pos2.

The following operands are available:
file The pathname of a file to be sorted, merged, or checked. If no file operands are specified, or if a file operand is -, the standard input is used.

A field is defined as a minimal sequence of characters followed by a field separator or a newline character. By default, the first blank space of a sequence of blank spaces acts as the field separator. All blank spaces in a sequence of blank spaces are considered as part of the next field; for example, all blank spaces at the beginning of a line are considered to be part of the first field.

Fields are specified by the -k field1[,field2] argument. A missing field2 argument defaults to the end of a line.

The arguments field1 and field2 have the form m.n followed by one or more of the options -b, -d, -f, -i, -n, -r. A field1 position specified by m.n (m,n > 0) is interpreted as the nth character in the mth field. A missing.n in field1 means ‘.1’, indicating the first character of the mth field; If the -b option is in effect, n is counted from the first non-blank character in the mth field; m.1b refers to the first non-blank character in the mth field.

A field2 position specified by m.n is interpreted as the nth character (including separators) of the mth field. A missing.n indicates the last character of the mth field; m = 0 designates the end of a line. Thus the option -k v.x,w.y is synonymous with the obsolescent option +v-1.x-1 -w-1.y; when y is omitted, -k v.x,w is synonymous with +v-1.x-1 -w+1.0. The obsolescent +pos1 -pos2 option is still supported, except for -w.0b, which has no -k equivalent.

ENVIRONMENT
If the following environment variable exists, it is utilized by sort.

TMPDIR
    Sort uses the contents of the TMPDIR environment variable as the path in which to store temporary files. Note that TMPDIR may be overridden by the -T option.

FILES
/var/tmp/sort.*
    Default temporary directories.
~ output#PID
    Temporary name for output if output already exists.

SEE ALSO
comm(1), uniq(1), join(1)

RETURN VALUES
Sort exits with one of the following values:
0:  normal behavior.
1:  on disorder (or non-uniqueness) with the -c option
2:  an error occurred.

BUGS
Lines longer than 65522 characters are discarded and processing continues. To sort files larger than 60Mb, use sort -H; files larger than 704Mb must be sorted in smaller pieces, then merged. To protect data sort -o calls link and unlink, and thus fails in protected directories.

HISTORY
A sort command appeared in AT&T UNIX.

NOTES
The current sort command uses lexicographic radix sorting, which requires that sort keys be kept in memory (as opposed to previous versions which used quick and merge sorts and did not.) Thus performance depends highly on efficient choice of sort keys, and the -b option and the field2 argument of the -k option should be used whenever possible. Similarly, sort -k1f is equivalent to sort -f and may take twice as long.