sort - sort or merge text files


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


The sort(1) 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(1) regards each input line as a single field.

The following options are available:

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

Only blank-space and alphanumeric characters are used in making comparisons.
Considers all lowercase characters that have uppercase equivalents to be the same for purposes of comparison.
Ignore all non-printable characters.
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.)
Reverse the sense of comparisons.

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

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 (discussed later in this topic). The -b option has no effect unless key fields are specified.
-t char
In this case, char is used as the field separator character. The initial char is not considered to be part of a field when determining key offsets. 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, and any number of continuous blanks count as a single field separator.
-T char
In this case, char is used as the record-separator character. The default record separator is newline (one line is one record). This should be used with discretion; -T<alphanumeric> usually produces undesirable results.
-k field1[,field2]
Designates the starting position, field1, and optional ending position, field2, of a key field. Counting starts at 1. The -k option replaces the obsolescent options +pos1 and -pos2.

You can specify more than one sorting field by specifying multiple -k options. The second field specified is only used to sort records where the first fields specified are identical, and so on.

The following operands are available:

The path name 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 -kfield1[,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 -kv.x,w.y is synonymous with the obsolescent option +v-1.x-1 w-1.y ; when y is omitted, -kv.x,w is synonymous with +v-1.x-1w+1.0. The obsolescent +pos1 -pos2 option is still supported, except for w.0b which has no -k equivalent.


The sort(1) utility makes use of the following files:

Default temporary directory, used if TMPDIR is not set.
Temporary name for output if output already exists.


The sort(1) utility exits with one of the following values:

Normal behavior.
On disorder (or non-uniqueness) with the -c option
An error occurred.


The current sort(1) 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). Performance therefore depends highly on the efficient choice of sort keys, and the -b option and the field2 argument of the -k option should be used whenever possible. Similarly, sort(1) -k1f is equivalent to sort(1) -f and might take twice as long.