sort(1) General Commands Manual sort(1)
NAME
sort - Sorts or merges files
SYNOPSIS
sort [-m] [-o output_file] [-Abdfinru] [-k keydef]... [-t character] [-T directory] [-y] [kilobytes] [-z record_size]... file...
sort -c [-u] [-Abdfinru] [-k keydef]... [-t character] [-T directory] [-y] [kilobytes] [-z record_size]... file...
The following older syntax is now maintained for backward compatibility, but may be withdrawn in future issues: sort [-Abcdfimnru] [-o out-
put_file] [-t character] [-T directory] [-y] [kilobytes] [-z record_size] [+fskip] [.cskip] [-fskip] [.cskip] [-bdfinr]... file...
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
sort: XCU5.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
OPTIONS
The -d, -f, -i, -n, and -r options override the default ordering rules. When ordering options appear independent of any key field specifi-
cations, the requested field ordering rules are applied globally to all sort keys. When attached to a specific key (see -k), the specified
ordering options override all global ordering options for that key. In the obsolescent forms, if one or more of these options follows a
+fskip option, it affects only the key field specified by that preceding option. [Tru64 UNIX] Sorts on a byte-by-byte basis using each
character's encoded value. On some systems, extended characters will be considered negative values, and so sort before ASCII characters.
If you are sorting ASCII characters in a non-C/POSIX locale, this option performs much faster. Ignores leading spaces and tabs when deter-
mining the starting and ending positions of a restricted sort key. If the -b option is specified before the first -k option, the -b option
is applied to all -k options on the command line; otherwise, the -b option can be independently attached to each -k field_start or
field_end argument. Checks that the input is sorted according to the ordering rules specified in the options and the collating sequence of
the current locale. No output is produced; only the exit code is affected. Specifies that only spaces and alphanumeric characters
(according to the current setting of LC_TYPE) are significant in comparisons. Treats all lowercase characters as their uppercase equiva-
lents (according to the current setting of LC_TYPE) for the purposes of comparison. Sorts only by printable characters (according to the
current setting of LC_TYPE). Specifies one or more (up to 50) restricted sort key field definitions. This option replaces the obsolescent
+fskip.cskip and -fskip.cskip options. A field comprises a maximal sequence of non-separating characters and, in the absence of the -t
option, any preceding field separator.
The format of a key field definition is as follows: field_start[type][,field_end[type]]
The field_start and field_end arguments define a key field that is restricted to a portion of the line, and type is a modifier spec-
ified by b, d, f, i, n, r, or t. The b modifier behaves like the -b option, but applies only to the field_start or field_end argu-
ment to which it is attached. The t modifier indicates that the key field is processed as CPU time. The other modifiers behave like
their corresponding options, but apply only to the key field to which they are attached; these modifiers have this effect if speci-
fied with field_start, field_end or both.
Modifiers attached to a field_start or field_end argument override any specifications made by the options. A missing field_end
argument means the last character of the line. When multiple sort keys are specified, it is advisable to specify a field_end argu-
ment to avoid possible confusion.
The field_start portion of the keydef argument takes the following form: field_number[.first_character]
Fields and characters within fields are numbered starting with 1. The field_number and first_character pieces, interpreted as posi-
tive decimal integers, specify the character to be used as part of a sort key. If first_character is not specified, the default is
the first character of the field.
The field_end portion of the keydef argument takes the following form: field_number[.last_character]
The field_number syntax is the same as that described for field_start. The last_character argument, interpreted as a nonnegative
decimal integer, specifies the last character to be used as part of the sort key. If last_character evaluates to 0 (zero) or is not
specified, the default is the last character of the field specified by field_number.
If -b is in effect, characters within a field are counted from the first nonspace character in the field. (This applies separately
to first_character and last_character.)
If -k is not specified, the default sort key is the entire line.
When there are multiple key fields, later keys are compared only after all earlier keys compare as equal. Except when the -u option
is specified, lines that otherwise compare as equal are ordered as though none of the options -d, -f, -i, -n, or -k were present
(but with -r still in effect, if it was specified) and with all bytes in the lines significant to the comparison.
The algorithm for the -k option can be summarized as follows:
/*
* -ka.b,c.d = if d==0 then +(a-1).(b-1) -c.d
* else +(a-1).(b-1) -(c-1).d
*/ Merges only (assumes sorted input). Sorts any initial numeric strings (including regular expressions consisting of optional
spaces, optional dashes, and zero (0) or more digits with optional radix character and thousands separator, as defined by the cur-
rent locale) by arithmetic value. An empty digit string is treated as zero; leading zeros and signs on zeros do not affect order-
ing. Only one period (.) can be used in numeric strings. All subsequent periods (.) and any character to the right of the period
(.) will be ignored. Directs output to output_file instead of standard output. The output_file can be the same as one of the input
files. Reverses the order of the specified sort. Sets the field separator character to character. The character argument is not
considered to be part of a field (although it can be included in a sort key). Each occurrence of character is significant (for
example, two consecutive occurrences of character delimit an empty field). To specify the tab character as the field separator, you
must enclose it in ' ' (single quotes).
The default field separator is one or more spaces. [Tru64 UNIX] Places all the temporary files that are created in directory.
Suppresses all but one in each set of equal lines (for example, lines whose sort keys match exactly). Ignored characters such as
leading tabs and spaces, and characters outside of sort keys are not considered in this type of comparison.
If used with the -c option, -u checks that there are no lines with duplicate keys, in addition to checking that the input file is
sorted. [Tru64 UNIX] Starts the sort command using kilobytes of main storage and adds storage as needed. (If kilobytes is less
than the minimum storage size or greater than the maximum, the minimum or maximum is used instead.) If the -y option is omitted,
the sort command starts with the default storage size; -y 0 starts with minimum storage, and -y (with no value) starts with the max-
imum storage. The amount of storage used by the sort command has a significant impact on performance. Sorting a small file in a
large amount of storage is wasteful. Prevents abnormal termination if lines being sorted are longer than the default buffer size
can handle. When the -c or -m options are specified, the sorting phase is omitted and a system default size buffer is used. If
sorted lines are longer than this size, sort terminates abnormally. The -z option specifies that the longest line be recorded in
the sort phase so that adequate buffers can be allocated in the merge phase. The record_size argument must be a value in bytes
equal to or greater than the number of bytes in the longest line to be merged. Specifies the start position of a key field. See
the -k option for a description of the current way to perform this operation. (Obsolescent)
The fskip variable specifies the number of fields to skip from the beginning of the input line, and the cskip variable specifies the
number of additional characters to skip to the right beyond that point. For both the starting point (+fskip.cskip) and the ending
point (-fskip.cskip) of a sort key, fskip is measured from the beginning of the input line, and cskip is measured from the last
field skipped. If you omit assumed. If you omit fskip, 0 (zero) is assumed. If you omit the ending field specifier
(-fskip.cskip), the end of the line is the end of the sort key.
You can supply more than one sort key by repeating +fskip.cskip and -fskip.cskip. In cases where you specify more than one sort
key, keys specified further to the right on the command line are compared only after all earlier keys are sorted. For example, if
the first key is to be sorted in numerical order and the second according to the collating sequence, all strings that start with the
number 1 are sorted according to the collating order before the strings that start with the number 2. Lines that are identical in
all keys are sorted with all characters significant. You can also specify different options for different sort keys in multiple
sort keys. Specifies the end position of a key field. See the -k option for a description of the current way to perform this oper-
ation. (Obsolescent)
DESCRIPTION
The sort command sorts lines in its input files and writes the result to standard output.
The sort command performs one of the following functions: Sorts lines of all the named files together and writes the result to the speci-
fied output. Merges lines of all the named (presorted) files together and writes the result to the specified output. Checks that a single
input file is correctly presorted.
Comparisons are based on one or more sort keys extracted from each line of input (or the entire line if no sort keys are specified), and
are performed using the collating sequence of the current locale.
The sort command treats all of its input files as one file when it performs the sort. A - (dash) in place of a file name specifies stan-
dard input. If you do not specify a file name, it sorts standard input.
The sort command can handle a variety of collation rules typically used in Western European languages, including primary/secondary sorting,
one-to-two character mapping, N-to-one character mapping, and ignore-character mapping. To summarize briefly:
Primary/Secondary Sorting
In this system, a group of characters all sort to the same primary location. If there is a tie, a secondary sort is applied. For example,
in French, the plain and accented a's all sort to the same primary location. If two strings collate to the same primary location, the sec-
ondary sort goes into effect. These words are in correct French order:
abord pre aprs pret azur
One-to-Two Character Mappings
This system requires that certain single characters be treated as if they were two characters. For example, in German, the (scharfes-S)
is collated as if it were ss.
N-to-One Character Mappings
Some languages treat a string of characters as if it were one single collating element. For example, in Spanish, the ch and ll sequences
are treated as their own elements within the alphabet. (ch comes between c and d in the alphabet, and ll comes between l and m.)
Ignore-Character Mappings
In some cases, certain characters may be ignored in collation. For example, if - were defined as an ignore-character, the strings re-
locate and relocate would sort to the same place. The results that you get from sort depend on the collating sequence as defined by the
current setting of the LC_COLLATE environment variable. The configuration files for collation and character classification information are
/usr/lib/nls/loc/src/locale.src. A field is one or more characters bounded by the beginning of a line and the current field separator, or
one or more characters bounded by a field separator on either side. The space character is the default field separator. Lines longer than
1024 bytes are truncated by sort. The maximum number of fields on a line is 50.
EXIT STATUS
The sort command returns the following exit values: All input files were output successfully, or -c was specified and the input file was
correctly sorted. Under the -c option, the file was not ordered as specified, or if the -c and -u options were both specified, two input
lines were found with equal keys. An error occurred.
EXAMPLES
The following examples apply to the C locale, unless it is specifically stated otherwise. To perform a simple sort, enter: sort fruits
This displays the contents of fruits sorted in ascending lexicographic order. This means that the characters in each column are
compared one by one, including spaces, digits, and special characters.
For instance, if fruits contains the text:
banana orange Persimmon apple %%banana apple ORANGE
Then sort fruits displays: %%banana ORANGE Persimmon apple apple banana orange
This order follows from the fact that in the ASCII collating sequence, symbols (such as %) precede uppercase letters, and all upper-
case letters precede the lowercase letters. If you are using a different collating order, your results may be different. To group
lines that contain uppercase and special characters with similar lowercase lines, and remove duplicate lines, enter: sort -d -f -u
fruits
The -u option tells sort to remove duplicate lines, making each line of the file unique. This displays: apple %%banana orange Per-
simmon
Not only was the duplicate apple removed, but banana and ORANGE were removed as well. The -d option told sort to ignore symbols, so
%%banana and banana were considered to be duplicate lines and banana was removed. The -f option told sort not to differentiate
between uppercase and lowercase, so ORANGE and orange were considered to be duplicate lines and ORANGE was removed.
When the -u option is used with input that contains nonidentical lines that are considered by sort (due to other options) to be
duplicates, there is no way to predict which lines sort will keep and which it will remove. To sort as in Example 2, but remove
duplicates unless capitalized or punctuated differently, enter: sort -u -k 1df -k 1 fruits
Options appearing between sort key specifiers apply only to the specifier preceding them. There are two sorts specified in this
command line. The -k 1df argument specifies the first sort, of the same type done with -d -f in Example 3. Then -k 1 performs
another comparison to distinguish lines that are not actually identical. This prevents -u, which applies to both sorts because it
precedes the first sort key specifier, from removing lines that are not exactly identical to other lines.
Given the fruits file shown in Example 1, the added -k 1 distinguishes %%banana from banana and ORANGE from orange. However, the two
instances of apple are exactly identical, so one of them is deleted. apple %%banana banana ORANGE orange Persimmon To specify a new
field separator, enter: sort -t : -k 2 vegetables
This sorts vegetables, comparing the text that follows the first colon on each line. The -t : option tells sort that colons sepa-
rate fields. The -k 2 argument tells sort to ignore the first field and to compare from the start of the second field to the end of
the line. If vegetables contains:
yams:104 turnips:8 potatoes:15 carrots:104 green beans:32 radishes:5 lettuce:15
then sort -t : -k 2 vegetables displays: carrots:104 yams:104 lettuce:15 potatoes:15 green beans:32 radishes:5 turnips:8
The numbers are not in ascending order. This is because a lexicographic sort compares each character from left to right. In other
words, 3 comes before 5 so 32 comes before 5. To sort on more than one field, enter: sort -t : -k 2n -k 1r vegetables
This performs a numeric sort on the second field (-k 2n) and then, within that ordering, sorts the first field in reverse collating
order (-k 1r). The output looks like this: radishes:5 turnips:8 potatoes:15 lettuce:15 green beans:32 yams:104 carrots:104
The lines are sorted in numeric order; when two lines have the same number, they appear in reverse collating order. To replace the
original file with the sorted text, enter: sort -o vegetables vegetables
The -o vegetables option stores the sorted output into the file vegetables. To collate using Spanish rules, set the LC_COLLATE (or
LANG) environment variable to a Spanish locale, and then use sort in the regular way, enter: sort sp.words
If an input file named sp.words contains the following Spanish words:
dama loro chapa canto mover chocolate curioso llanura
The sorted file looks like this: canto curioso chapa chocolate dama loro llanura mover
If you sort the file in the default C locale, the output looks like this: canto chapa chocolate curioso dama llanura loro mover
ENVIRONMENT VARIABLES
The following environment variables affect the execution of sort: Provides a default value for the internationalization variables that are
unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization vari-
ables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value,
overrides the values of all the other internationalization variables. Determines the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as opposed to multibyte characters in arguments) and the behavior of character classi-
fication for the -b, -d, -f, -i, and -n options. Determines the locale for the format and contents of diagnostic messages written to stan-
dard error. Determines the location of message catalogues for the processing of LC_MESSAGES.
FILES
Configuration files
SEE ALSO
Commands: comm(1), join(1), uniq(1)
Functions: setlocale(3), tolower(3)
Files: locale(4)
Standards: standards(5)
sort(1)