Tribblix: manual page: sort.1

SORT(1) User Commands SORT(1)

NAME

sort - sort, merge, or sequence check text files

SYNOPSIS

/usr/bin/sort [-bcdfimMnru] [-k keydef] [-o output]
[-S kmem] [-t char] [-T directory] [-y [kmem]]
[-z recsz] [+pos1 [-pos2]] [file]...

/usr/xpg4/bin/sort [-bcdfimMnru] [-k keydef] [-o output]
[-S kmem] [-t char] [-T directory] [-y [kmem]]
[-z recsz] [+pos1 [-pos2]] [file]...

DESCRIPTION

The sort command sorts lines of all the named files together and
writes the result on the standard output.

Comparisons are based on one or more sort keys extracted from each
line of input. By default, there is one sort key, the entire input
line. Lines are ordered according to the collating sequence of the
current locale.

OPTIONS

The following options alter the default behavior:

/usr/bin/sort
-c
Checks that the single input file is ordered as specified by
the arguments and the collating sequence of the current locale.
The exit code is set and no output is produced unless the file
is out of sort.

/usr/xpg4/bin/sort
-c
Same as /usr/bin/sort except no output is produced
under any circumstances.

-m
Merges only. The input files are assumed to be
already sorted.

-o output
Specifies 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.

-S kmem
Specifies the maximum amount of swap-based memory
used for sorting, in kilobytes (the default unit).
kmem can also be specified directly as a number of
bytes (b), kilobytes (k), megabytes (m), gigabytes
(g), or terabytes (t); or as a percentage (%) of the
installed physical memory.

-T directory
Specifies the directory in which to place temporary
files.

-u
Unique: suppresses all but one in each set of lines
having equal keys. If used with the -c option, checks
that there are no lines with duplicate keys in
addition to checking that the input file is sorted.

-y kmem
(obsolete). This option was used to specify the
amount of main memory initially used by sort. Its
functionality is not appropriate for a virtual memory
system; memory usage for sort is now specified using
the -S option.

-z recsz
(obsolete). This option was used to prevent abnormal
termination when lines longer than the system-
dependent default buffer size are encountered.
Because sort automatically allocates buffers large
enough to hold the longest line, this option has no
effect.

Ordering Options

The default sort order depends on the value of LC_COLLATE. If
LC_COLLATE is set to C, sorting is in ASCII order. If LC_COLLATE is
set to en_US, sorting is case insensitive except when the two strings
are otherwise equal and one has an uppercase letter earlier than the
other. Other locales have other sort orders.

The following options override the default ordering rules. When
ordering options 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 Sort Key Options), 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 +pos1 option, it affects only the key field specified by
that preceding option.

-d
Dictionary order: only letters, digits, and blanks (spaces and
tabs) are significant in comparisons.

-f
Folds lower-case letters into upper case.

-i
Ignores non-printable characters.

-M
Compares as months. The first three non-blank characters of the
field are folded to upper case and compared. For example, in
English the sorting order is "JAN" < "FEB" < ... < "DEC".
Invalid fields compare low to "JAN". The -M option implies the
-b option (see below).

-n
Restricts the sort key to an initial numeric string, consisting
of optional blank characters, optional minus sign, and zero or
more digits with an optional radix character and thousands
separators (as defined in the current locale), which is sorted
by arithmetic value. An empty digit string is treated as zero.
Leading zeros and signs on zeros do not affect ordering.

-r
Reverses the sense of comparisons.

Field Separator Options

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

-b
Ignores leading blank characters when determining the
starting and ending positions of a restricted sort key. If
the -b option is specified before the first sort key
option, it is applied to all sort key options. Otherwise,
the -b option can be attached independently to each -k
field_start, field_end, or +pos1 or -pos2 option-argument
(see below).

-t char
Use char as the field separator character. char is not
considered to be part of a field (although it can be
included in a sort key). Each occurrence of char is
significant (for example, <char><char> delimits an empty
field). If -t is not specified, blank characters are used
as default field separators; each maximal non-empty
sequence of blank characters that follows a non-blank
character is a field separator.

Sort Key Options

Sort keys can be specified using the options:

-k keydef
The keydef argument is a restricted sort key field
definition. The format of this definition is:

-k field_start [type] [,field_end [type] ]

where:

field_start and field_end

define a key field restricted to a portion of
the line.

type

is a modifier from the list of characters
bdfiMnr. The b modifier behaves like the -b
option, but applies only to the field_start or
field_end to which it is attached and
characters within a field are counted from the
first non-blank character in the field. (This
applies separately to first_character and
last_character.) The other modifiers behave
like the corresponding options, but apply only
to the key field to which they are attached.
They have this effect if specified with
field_start, field_end or both. If any
modifier is attached to a field_start or to a
field_end, no option applies to either.

When there are multiple key fields, later keys are
compared only after all earlier keys compare
equal. Except when the -u option is specified,
lines that otherwise compare equal are ordered as
if 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 notation:

-k field_start[type][,field_end[type]]

defines a key field that begins at field_start and
ends at field_end inclusive, unless field_start
falls beyond the end of the line or after
field_end, in which case the key field is empty. A
missing field_end means the last character of the
line.

A field comprises a maximal sequence of non-
separating characters and, in the absence of
option -t, any preceding field separator.

The field_start portion of the keydef option-
argument has the form:

field_number[.first_character]

Fields and characters within fields are numbered
starting with 1. field_number and
first_character, interpreted as positive decimal
integers, specify the first character to be used
as part of a sort key. If .first_character is
omitted, it refers to the first character of the
field.

The field_end portion of the keydef option-
argument has the form:

field_number[.last_character]

The field_number is as described above for
field_start. last_character, interpreted as a
non-negative decimal integer, specifies the last
character to be used as part of the sort key. If
last_character evaluates to zero or
.last_character is omitted, it refers to the last
character of the field specified by field_number.

If the -b option or b type modifier is in effect,
characters within a field are counted from the
first non-blank character in the field. (This
applies separately to first_character and
last_character.)

[+pos1 [-pos2]]
(obsolete). Provide functionality equivalent to
the -kkeydef option.

pos1 and pos2 each have the form m.n optionally
followed by one or more of the flags bdfiMnr. A
starting position specified by +m.n is interpreted
to mean the n+1st character in the m+1st field. A
missing .n means .0, indicating the first
character of the m+1st field. If the b flag is in
effect n is counted from the first non-blank in
the m+1st field; +m.0b refers to the first non-
blank character in the m+1st field.

A last position specified by -m.n is interpreted
to mean the nth character (including separators)
after the last character of the mth field. A
missing .n means .0, indicating the last character
of the mth field. If the b flag is in effect n is
counted from the last leading blank in the m+1st
field; -m.1b refers to the first non-blank in the
m+1st field.

The fully specified +pos1 -pos2 form with type
modifiers T and U:

+w.xT -y.zU

is equivalent to:

undefined (z==0 & U contains b & -t is present)
-k w+1.x+1T,y.0U (z==0 otherwise)
-k w+1.x+1T,y+1.zU (z > 0)

Implementations support at least nine occurrences
of the sort keys (the -k option and obsolescent
+pos1 and -pos2) which are significant in command
line order. If no sort key is specified, a default
sort key of the entire line is used.

OPERANDS

The following operand is supported:

file
A 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.

USAGE

See largefile(7) for the description of the behavior of sort when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

EXAMPLES

In the following examples, first the preferred and then the obsolete
way of specifying sort keys are given as an aid to understanding the
relationship between the two forms.

Example 1: Sorting with the Second Field as a sort Key

Either of the following commands sorts the contents of infile with
the second field as the sort key:

example% sort -k 2,2 infile
example% sort +1 -2 infile

Example 2: Sorting in Reverse Order

Either of the following commands sorts, in reverse order, the
contents of infile1 and infile2, placing the output in outfile and
using the second character of the second field as the sort key
(assuming that the first character of the second field is the field
separator):

example% sort -r -o outfile -k 2.2,2.2 infile1 infile2
example% sort -r -o outfile +1.1 -1.2 infile1 infile2

Example 3: Sorting Using a Specified Character in One of the Files

Either of the following commands sorts the contents of infile1 and
infile2 using the second non-blank character of the second field as
the sort key:

example% sort -k 2.2b,2.2b infile1 infile2
example% sort +1.1b -1.2b infile1 infile2

Example 4: Sorting by Numeric User ID

Either of the following commands prints the passwd(5) file (user
database) sorted by the numeric user ID (the third colon-separated
field):

example% sort -t : -k 3,3n /etc/passwd
example% sort -t : +2 -3n /etc/passwd

Example 5: Printing Sorted Lines Excluding Lines that Duplicate a

Field

Either of the following commands prints the lines of the already
sorted file infile, suppressing all but one occurrence of lines
having the same third field:

example% sort -um -k 3.1,3.0 infile
example% sort -um +2.0 -3.0 infile

Example 6: Sorting by Host IP Address

Either of the following commands prints the hosts(5) file (IPv4 hosts
database), sorted by the numeric IP address (the first four numeric
fields):

example$ sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n /etc/hosts
example$ sort -t . +0 -1n +1 -2n +2 -3n +3 -4n /etc/hosts

Since '.' is both the field delimiter and, in many locales, the
decimal separator, failure to specify both ends of the field leads to
results where the second field is interpreted as a fractional portion
of the first, and so forth.

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment
variables that affect the execution of sort: LANG, LC_ALL,
LC_COLLATE, LC_MESSAGES, and NLSPATH.

LC_CTYPE
Determine the locale for the interpretation of
sequences of bytes of text data as characters (for
example, single- versus multi-byte characters in
arguments and input files) and the behavior of
character classification for the -b, -d, -f, -i and -n
options.

LC_NUMERIC
Determine the locale for the definition of the radix
character and thousands separator for the -n option.

EXIT STATUS

The following exit values are returned:

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

1
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.

>1
An error occurred.

FILES

/var/tmp/stm???
Temporary files

ATTRIBUTES

DIAGNOSTICS

Comments and exits with non-zero status for various trouble
conditions (for example, when input lines are too long), and for
disorders discovered under the -c option.

NOTES

When the last line of an input file is missing a new-line character,
sort appends one, prints a warning message, and continues.

sort does not guarantee preservation of relative line ordering on
equal keys.

One can tune sort performance for a specific scenario using the -S
option. However, one should note in particular that sort has greater
knowledge of how to use a finite amount of memory for sorting than
the virtual memory system. Thus, a sort invoked to request an
extremely large amount of memory via the -S option could perform
extremely poorly.

As noted, certain of the field modifiers (such as -M and -d) cause
the interpretation of input data to be done with reference to locale-
specific settings. The results of this interpretation can be
unexpected if one's expectations are not aligned with the conventions
established by the locale. In the case of the month keys, sort does
not attempt to compensate for approximate month abbreviations. The
precise month abbreviations from nl_langinfo(3C) or strftime(3C) are
the only ones recognized. For printable or dictionary order, if these
concepts are not well-defined by the locale, an empty sort key might
be the result, leading to the next key being the significant one for
determining the appropriate ordering.

November 19, 2001 SORT(1)