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|
sort(P) sort(P)
NAME
sort - sort, merge, or sequence check text files
SYNOPSIS
sort [-m][-o output][-bdfinru][-t char][-k keydef]...
[file...]
sort -c [-bdfinru][-t char][-k keydef][file]
DESCRIPTION
The sort utility shall perform one of the following
functions:
Sort lines of all the named files together and write the
result to the specified output.
Merge lines of all the named (presorted) files together
and write the result to the specified output.
Check that a single input file is correctly presorted.
Comparisons shall be based on one or more sort keys
extracted from each line of input (or, if no sort keys
are specified, the entire line up to, but not including,
the terminating <newline>), and shall be performed using
the collating sequence of the current locale.
OPTIONS
The sort utility shall conform to the Base Definitions
volume of IEEE Std 1003.1-2001, Section 12.2, Utility
Syntax Guidelines, and the -k keydef option should fol-
low the -b, -d, -f, -i, -n, and -r options.
The following options shall be supported:
-c Check that the single input file is ordered as
specified by the arguments and the collating
sequence of the current locale. No output shall
be produced; only the exit code shall be
affected.
-m Merge only; the input file shall be assumed to be
already sorted.
-o output
Specify 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.
-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, in addition to checking that the input file
is sorted.
The following options shall override the default order-
ing rules. When ordering options appear independent of
any key field specifications, the requested field order-
ing rules shall be applied globally to all sort keys.
When attached to a specific key (see -k), the specified
ordering options shall override all global ordering
options for that key.
-d Specify that only <blank>s and alphanumeric char-
acters, according to the current setting of
LC_CTYPE , shall be significant in comparisons.
The behavior is undefined for a sort key to which
-i or -n also applies.
-f Consider all lowercase characters that have
uppercase equivalents, according to the current
setting of LC_CTYPE , to be the uppercase equiva-
lent for the purposes of comparison.
-i Ignore all characters that are non-printable,
according to the current setting of LC_CTYPE .
-n Restrict the sort key to an initial numeric
string, consisting of optional <blank>s, optional
minus sign, and zero or more digits with an
optional radix character and thousands separators
(as defined in the current locale), which shall
be sorted by arithmetic value. An empty digit
string shall be treated as zero. Leading zeros
and signs on zeros shall not affect ordering.
-r Reverse the sense of comparisons.
The treatment of field separators can be altered using
the options:
-b Ignore leading <blank>s when determining the
starting and ending positions of a restricted
sort key. If the -b option is specified before
the first -k option, it shall be applied to all
-k options. Otherwise, the -b option can be
attached independently to each -k field_start or
field_end option-argument (see below).
-t char
Use char as the field separator character; char
shall not be considered to be part of a field
(although it can be included in a sort key). Each
occurrence of char shall be significant (for
example, <char><char> delimits an empty field).
If -t is not specified, <blank>s shall be used as
default field separators; each maximal non-empty
sequence of <blank>s that follows a non- <blank>
shall be a field separator.
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:
field_start[type][,field_end[type]]
where field_start and field_end define a key field
restricted to a portion of the line (see the EXTENDED
DESCRIPTION section), and type is a modifier from the
list of characters 'b' , 'd' , 'f' , 'i' , 'n' , 'r' .
The 'b' modifier shall behave like the -b option, but
shall apply only to the field_start or field_end to
which it is attached. The other modifiers shall behave
like the corresponding options, but shall apply only to
the key field to which they are attached; they shall
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 shall apply to
either. Implementations shall support at least nine
occurrences of the -k option, which shall be significant
in command line order. If no -k option is specified, a
default sort key of the entire line shall be used.
When there are multiple key fields, later keys shall be
compared only after all earlier keys compare equal.
Except when the -u option is specified, lines that oth-
erwise compare equal shall be 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 order in
which lines that still compare equal are written is
unspecified.
OPERANDS
The following operand shall be supported:
file A 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 shall
be used.
STDIN
The standard input shall be used only if no file oper-
ands are specified, or if a file operand is '-' . See
the INPUT FILES section.
INPUT FILES
The input files shall be text files, except that the
sort utility shall add a <newline> to the end of a file
ending with an incomplete last line.
ENVIRONMENT VARIABLES
The following environment variables shall affect the
execution of sort:
LANG Provide a default value for the internationaliza-
tion variables that are unset or null. (See the
Base Definitions volume of IEEE Std 1003.1-2001,
Section 8.2, Internationalization Variables for
the precedence of internationalization variables
used to determine the values of locale cate-
gories.)
LC_ALL If set to a non-empty string value, override the
values of all the other internationalization
variables.
LC_COLLATE
Determine the locale for ordering rules.
LC_CTYPE
Determine the locale for the interpretation of
sequences of bytes of text data as characters
(for example, single-byte as opposed to multi-
byte characters in arguments and input files) and
the behavior of character classification for the
-b, -d, -f, -i, and -n options.
LC_MESSAGES
Determine the locale that should be used to
affect the format and contents of diagnostic mes-
sages written to standard error.
LC_NUMERIC
Determine the locale for the definition of the
radix character and thousands separator for the
-n option.
NLSPATH
Determine the location of message catalogs for
the processing of LC_MESSAGES .
ASYNCHRONOUS EVENTS
Default.
STDOUT
Unless the -o or -c options are in effect, the standard
output shall contain the sorted input.
STDERR
The standard error shall be used for diagnostic mes-
sages. A warning message about correcting an incomplete
last line of an input file may be generated, but need
not affect the final exit status.
OUTPUT FILES
If the -o option is in effect, the sorted input shall be
written to the file output.
EXTENDED DESCRIPTION
The notation:
-k field_start[type][,field_end[type]]
shall define 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 shall
mean the last character of the line.
A field comprises a maximal sequence of non-separating
characters and, in the absence of option -t, any preced-
ing field separator.
The field_start portion of the keydef option-argument
shall have the form:
field_number[.first_character]
Fields and characters within fields shall be numbered
starting with 1. The field_number and first_character
pieces, interpreted as positive decimal integers, shall
specify the first character to be used as part of a sort
key. If .first_character is omitted, it shall refer to
the first character of the field.
The field_end portion of the keydef option-argument
shall have the form:
field_number[.last_character]
The field_number shall be as described above for
field_start. The last_character piece, interpreted as a
non-negative decimal integer, shall specify the last
character to be used as part of the sort key. If
last_character evaluates to zero or .last_character is
omitted, it shall refer to the last character of the
field specified by field_number.
If the -b option or b type modifier is in effect, char-
acters within a field shall be counted from the first
non- <blank> in the field. (This shall apply separately
to first_character and last_character.)
EXIT STATUS
The following exit values shall be 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.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The default value for -t, <blank>, has different proper-
ties from, for example, -t "<space>". If a line con-
tains:
<space><space>foo
the following treatment would occur with default separa-
tion as opposed to specifically selecting a <space>:
Field Default -t "<space>"
1 <space><space>foo empty
2 empty empty
3 empty foo
The leading field separator itself is included in a
field when -t is not used. For example, this command
returns an exit status of zero, meaning the input was
already sorted:
sort -c -k 2 <<eof
y<tab>b
x<space>a
eof
(assuming that a <tab> precedes the <space> in the cur-
rent collating sequence). The field separator is not
included in a field when it is explicitly set via -t.
This is historical practice and allows usage such as:
sort -t "|" -k 2n <<eof
Atlanta|425022|Georgia
Birmingham|284413|Alabama
Columbia|100385|South Carolina
eof
where the second field can be correctly sorted numeri-
cally without regard to the non-numeric field separator.
The wording in the OPTIONS section clarifies that the
-b, -d, -f, -i, -n, and -r options have to come before
the first sort key specified if they are intended to
apply to all specified keys. The way it is described in
this volume of IEEE Std 1003.1-2001 matches historical
practice, not historical documentation. The results are
unspecified if these options are specified after a -k
option.
The -f option might not work as expected in locales
where there is not a one-to-one mapping between an
uppercase and a lowercase letter.
EXAMPLES
The following command sorts the contents of infile with
the second field as the sort key:
sort -k 2,2 infile
The following command sorts, in reverse order, the con-
tents of infile1 and infile2, placing the output in out-
file 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):
sort -r -o outfile -k 2.2,2.2 infile1 infile2
The following command sorts the contents of infile1 and
infile2 using the second non- <blank> of the second
field as the sort key:
sort -k 2.2b,2.2b infile1 infile2
The following command prints the System V password file
(user database) sorted by the numeric user ID (the third
colon-separated field):
sort -t : -k 3,3n /etc/passwd
The following command prints the lines of the already
sorted file infile, suppressing all but one occurrence
of lines having the same third field:
sort -um -k 3.1,3.0 infile
RATIONALE
Examples in some historical documentation state that
options -um with one input file keep the first in each
set of lines with equal keys. This behavior was deemed
to be an implementation artifact and was not standard-
ized.
The -z option was omitted; it is not standard practice
on most systems and is inconsistent with using sort to
sort several files individually and then merge them
together. The text concerning -z in historical documen-
tation appeared to require implementations to determine
the proper buffer length during the sort phase of opera-
tion, but not during the merge.
The -y option was omitted because of non-portability.
The -M option, present in System V, was omitted because
of non-portability in international usage.
An undocumented -T option exists in some implementa-
tions. It is used to specify a directory for intermedi-
ate files. Implementations are encouraged to support
the use of the TMPDIR environment variable instead of
adding an option to support this functionality.
The -k option was added to satisfy two objections.
First, the zero-based counting used by sort is not con-
sistent with other utility conventions. Second, it did
not meet syntax guideline requirements.
Historical documentation indicates that "setting -n
implies -b". The description of -n already states that
optional leading <blank>s are tolerated in doing the
comparison. If -b is enabled, rather than implied, by
-n, this has unusual side effects. When a character off-
set is used in a column of numbers (for example, to sort
modulo 100), that offset is measured relative to the
most significant digit, not to the column. Based upon a
recommendation from the author of the original sort
utility, the -b implication has been omitted from this
volume of IEEE Std 1003.1-2001, and an application wish-
ing to achieve the previously mentioned side effects has
to code the -b flag explicitly.
FUTURE DIRECTIONS
None.
SEE ALSO
comm , join , uniq , the System Interfaces volume of
IEEE Std 1003.1-2001, toupper()
COPYRIGHT
Portions of this text are reprinted and reproduced in
electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operat-
ing System Interface (POSIX), The Open Group Base Speci-
fications Issue 6, Copyright (C) 2001-2003 by the Insti-
tute of Electrical and Electronics Engineers, Inc and
The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be
obtained online at http://www.open-
group.org/unix/online.html .
POSIX 2003 sort(P)
|
