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The following older syntax is now maintained for backward compatibility, but may be withdrawn in future issues: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 output_file] [-t character] [-T directory] [-y][kilobytes] [-z record_size] [+fskip][.cskip] [-fskip][.cskip] [-bdfinr] ...  file ... 

FLAGS

The -d, -f, -i, -n, and -r flags override the default ordering rules.  When ordering flags appear independent of any key field specifications, the requested field ordering rules are applied globally to all sort keys.  When attached to a specific key (see -k), the specified ordering flags override all global ordering flags for that key.  In the obsolescent forms, if one or more of these flags follows a +fskip flag, it affects only the key field specified by that preceding flag. 

-ASorts 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 flag performs much faster. 

-bIgnores leading spaces and tabs when determining the starting and ending positions of a restricted sort key.  If the -b flag is specified before the first -k flag, the -b flag is applied to all -k flags on the command line; otherwise, the -b flag can be independently attached to each -k field_start or field_end argument. 

-cChecks that the input is sorted according to the ordering rules specified in the flags and the collating sequence of the current locale.  No output is produced; only the exit code is affected. 

-dSpecifies that only spaces and alphanumeric characters (according to the current setting of LC_TYPE) are significant in comparisons. 

-fTreats all lowercase characters as their uppercase equivalents (according to the current setting of LC_TYPE) for the purposes of comparison. 

-iSorts only by printable characters (according to the current setting of LC_TYPE). 

-k keydef
Specifies one or more (up to 10) restricted sort key field definitions.  This flag replaces the obsolescent +fskip.cskip and -fskip.cskip flags.  A field comprises a maximal sequence of non-separating characters and, in the absence of the -t flag, any preceding field separator. 

The format of a key field definition is as follows:

field_start[type][,field_end[type]]

where 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 specified by b, d, f, i, n, or r.  The b modifier behaves like the -b flag, but applies only to the field_start or field_end argument to which it is attached.  The other modifiers behave like their corresponding flags, but apply only to the key field to which they are attached; these modifiers have this effect if specified with field_start, field_end or both. 

Modifiers attached to a field_start or field_end argument override any specifications made by the flags.  A missing field_end argument means the last character of the line. 

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 positive 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 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 flag is specified, lines that otherwise compare as equal are ordered as though none of the flags -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 flag 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
 ∗/

-mMerges only (assumes sorted input). 

-nSorts 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 current locale) by arithmetic value.  An empty digit string is treated as zero; leading zeros and signs on zeros do not affect ordering.  Only one period (.) can be used in numeric strings.  All subsequent periods (.) and any character to the right of the period (.) will be ignored. 

-o output_file
Directs output to output_file instead of standard output.  The output_file can be the same as one of the input files. 

-rReverses the order of the specified sort. 

-t character
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. 

-T directory
Places all the temporary files that are created in directory. 

-uSuppresses 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 flag, -u checks that there are no lines with duplicate keys, in addition to checking that the input file is sorted. 

-y [kilobytes]
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 flag 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 maximum 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. 

-z record_size
Prevents abnormal termination if lines being sorted are longer than the default buffer size can handle.  When the -c or -m flags 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. 

+fskip.cskip
Specifies the start position of a key field.  See the -k flag 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 .cskip, .0 (zero) is 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 flags for different sort keys in multiple sort keys. 

-fskip.cskip
Specifies the end position of a key field.  See the -k flag for a description of the current way to perform this operation.  (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:

     1.Sorts lines of all the named files together and writes the result to the specified output. 

     2.Merges lines of all the named (presorted) files together and writes the result to the specified output. 

     3.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 filename specifies standard input.  If you do not specify a filename, 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 secondary sort goes into effect.  These words are in correct French order:

abord
ˆpre
aprs
ˆpret
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 ß (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 10. 

EXAMPLES

The following examples apply to the C locale, unless it is specifically stated otherwise. 

     1.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 uppercase letters precede the lowercase letters.  If you are using a different collating order, your results may be different. 

     2.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 flag tells sort to remove duplicate lines, making each line of the file unique.  This displays:

apple
%%banana
orange
Persimmon

Note that not only was the duplicate apple removed, but banana and ORANGE were removed as well.  The -d flag told sort to ignore symbols, so %%banana and banana were considered to be duplicate lines and banana was removed.  The -f flag 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 flag is used with input that contains nonidentical lines that are considered by sort (due to other flags) to be duplicates, there is no way to predict which lines sort will keep and which it will remove. 

     3.To sort as in Example 2, but remove duplicates unless capitalized or punctuated differently, enter:

sort -u -k 1df -k 1  fruits

Flags 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

     4.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 separate 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

Note that 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. 

     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. 

     6.To replace the original file with the sorted text, enter:

sort  -o  vegetables  vegetables

The -o vegetables flag stores the sorted output into the file vegetables. 

     7.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

FILES

/usr/lib/nls/loc/src/locale.srcConfiguration files. 

EXIT VALUES

The sort command returns the following exit values:

0All input files were output successfully, or -c was specified and the input file was correctly sorted. 

1Under the -c flag, the file was not ordered as specified, or if the -c and -u flags were both specified, two input lines were found with equal keys. 

>1An error occurred. 

RELATED INFORMATION

Commands:  comm(1), join(1), uniq(1). 

Functions: setlocale(3)

Files:  locale(4).