sort: Sort text filessort sorts, merges, or compares all the lines from the given
files, or standard input if none are given or for a file of
‘-’. By default, sort writes the results to standard
output. Synopsis:
sort [option]… [file]…
Many options affect how sort compares lines; if the results
are unexpected, try the --debug option to see what happened.
A pair of lines is compared as follows:
sort compares each pair of fields (see --key), in the
order specified on the command line, according to the associated
ordering options, until a difference is found or no fields are left.
If no key fields are specified, sort uses a default key of
the entire line. Finally, as a last resort when all keys compare
equal, sort compares entire lines as if no ordering options
other than --reverse (-r) were specified. The
--stable (-s) option disables this last-resort
comparison so that lines in which all fields compare equal are left
in their original relative order. The --unique
(-u) option also disables the last-resort comparison.
Unless otherwise specified, all comparisons use the character collating
sequence specified by the LC_COLLATE locale.1
A line’s trailing newline is not part of the line for comparison
purposes. If the final byte of an input file is not a newline, GNU
sort silently supplies one. GNU sort (as
specified for all GNU utilities) has no limit on input line length or
restrictions on bytes allowed within lines.
sort has three modes of operation: sort (the default), merge,
and check for order. The following options change the operation
mode:
Check whether the given file is already sorted: if it is not all sorted, print a diagnostic containing the first out-of-order line and exit with a status of 1. Otherwise, exit successfully. At most one input file can be given.
Exit successfully if the given file is already sorted, and exit with status 1 otherwise. At most one input file can be given. This is like -c, except it does not print a diagnostic.
Merge the given files by sorting them as a group. Each input file must always be individually sorted. It always works to sort instead of merge; merging is provided because it is faster, in the case where it works.
Exit status:
0 if no error occurred 1 if invoked with -c or -C and the input is not sorted 2 if an error occurred
If the environment variable TMPDIR is set, sort uses its
value as the directory for temporary files instead of /tmp. The
--temporary-directory (-T) option in turn overrides
the environment variable.
The following options affect the ordering of output lines. They may be
specified globally or as part of a specific key field. If no key
fields are specified, global options apply to comparison of entire
lines; otherwise the global options are inherited by key fields that do
not specify any special options of their own. In pre-POSIX
versions of sort, global options affect only later key fields,
so portable shell scripts should specify global options first.
Ignore leading blanks when finding sort keys in each line.
By default a blank is a space or a tab, but the LC_CTYPE locale
can change this. Blanks may be ignored by your locale’s collating
rules, but without this option they will be significant for character
positions specified in keys with the -k option.
Sort in phone directory order: ignore all characters except
letters, digits and blanks when sorting.
By default letters and digits are those of ASCII and a blank
is a space or a tab, but the LC_CTYPE locale can change this.
Fold lowercase characters into the equivalent uppercase characters when
comparing so that, for example, ‘b’ and ‘B’ sort as equal.
The LC_CTYPE locale determines character types.
When used with --unique those lower case equivalent lines are
thrown away. (There is currently no way to throw away the upper case
equivalent instead. (Any --reverse given would only affect
the final result, after the throwing away.))
Sort numerically, converting a prefix of each line to a long double-precision floating point number. See Floating point numbers. Do not report overflow, underflow, or conversion errors. Use the following collating sequence:
Use this option only if there is no alternative; it is much slower than --numeric-sort (-n) and it can lose information when converting to floating point.
You can use this option to sort hexadecimal numbers prefixed with ‘0x’ or ‘0X’, where those numbers are not fixed width, or of varying case. However for hex numbers of consistent case, and left padded with ‘0’ to a consistent width, a standard lexicographic sort will be faster.
Sort numerically, first by numeric sign (negative, zero, or positive);
then by SI suffix (either empty, or ‘k’ or ‘K’, or
one of ‘MGTPEZYRQ’, in that order; see Block size); and finally
by numeric value. For example, ‘1023M’ sorts before ‘1G’
because ‘M’ (mega) precedes ‘G’ (giga) as an SI
suffix. This option sorts values that are consistently scaled to the
nearest suffix, regardless of whether suffixes denote powers of 1000
or 1024, and it therefore sorts the output of any single invocation of
the df, du, or ls commands that are
invoked with their --human-readable or --si options.
The syntax for numbers is the same as for the --numeric-sort
option; the SI suffix must immediately follow the number.
To sort more accurately, you can use the numfmt command
to reformat numbers to human format after the sort.
Ignore nonprinting characters.
The LC_CTYPE locale determines character types.
This option has no effect if the stronger --dictionary-order
(-d) option is also given.
An initial string, consisting of any amount of blanks, followed
by a month name abbreviation, is folded to UPPER case and
compared in the order ‘JAN’ < ‘FEB’ < … < ‘DEC’.
Invalid names compare low to valid names. The LC_TIME locale
category determines the month spellings.
By default a blank is a space or a tab, but the LC_CTYPE locale
can change this.
Sort numerically. The number begins each line and consists of optional blanks, an optional ‘-’ sign, and zero or more digits possibly separated by thousands separators, optionally followed by a decimal-point character and zero or more digits. An empty number is treated as ‘0’. Signs on zeros and leading zeros do not affect ordering.
Comparison is exact; there is no rounding error.
The LC_CTYPE locale specifies which characters are blanks and
the LC_NUMERIC locale specifies the thousands separator and
decimal-point character. In the C locale, spaces and tabs are blanks,
there is no thousands separator, and ‘.’ is the decimal point.
Neither a leading ‘+’ nor exponential notation is recognized. To compare such strings numerically, use the --general-numeric-sort (-g) option.
Sort by version name and number. It behaves like a standard sort, except that each sequence of decimal digits is treated numerically as an index/version number. (See Version sort ordering.)
Reverse the result of comparison, so that lines with greater key values appear earlier in the output instead of later.
Sort by hashing the input keys and then sorting the hash values.
Choose the hash function at random, ensuring that it is free of
collisions so that differing keys have differing hash values. This is
like a random permutation of the inputs (see shuf: Shuffling text),
except that keys with the same value sort together.
If multiple random sort fields are specified, the same random hash
function is used for all fields. To use different random hash
functions for different fields, you can invoke sort more
than once.
The choice of hash function is affected by the --random-source option.
Other options are:
Compress any temporary files with the program prog.
With no arguments, prog must compress standard input to standard output, and when given the -d option it must decompress standard input to standard output.
Terminate with an error if prog exits with nonzero status.
White space and the backslash character should not appear in prog; they are reserved for future use.
Disallow processing files named on the command line, and instead process
those named in file file; each name being terminated by a zero byte
(ASCII NUL).
This is useful
when the list of file names is so long that it may exceed a command line
length limitation.
In such cases, running sort via xargs is undesirable
because it splits the list into pieces and makes sort print
sorted output for each sublist rather than for the entire list.
One way to produce a list of ASCII NUL terminated file
names is with GNU
find, using its -print0 predicate.
If file is ‘-’ then the ASCII NUL terminated
file names are read from standard input.
Specify a sort field that consists of the part of the line between pos1 and pos2 (or the end of the line, if pos2 is omitted), inclusive.
In its simplest form pos specifies a field number (starting with 1), with fields being separated by runs of blank characters, and by default those blanks being included in the comparison at the start of each field. To adjust the handling of blank characters see the -b and -t options.
More generally, each pos has the form ‘f[.c][opts]’, where f is the number of the field to use, and c is the number of the first character from the beginning of the field. Fields and character positions are numbered starting with 1; a character position of zero in pos2 indicates the field’s last character. If ‘.c’ is omitted from pos1, it defaults to 1 (the beginning of the field); if omitted from pos2, it defaults to 0 (the end of the field). opts are ordering options, allowing individual keys to be sorted according to different rules; see below for details. Keys can span multiple fields.
Example: To sort on the second field, use --key=2,2 (-k 2,2). See below for more notes on keys and more examples. See also the --debug option to help determine the part of the line being used in the sort.
Highlight the portion of each line used for sorting. Also issue warnings about questionable usage to standard error.
Merge at most nmerge inputs at once.
When sort has to merge more than nmerge inputs,
it merges them in groups of nmerge, saving the result in
a temporary file, which is then used as an input in a subsequent merge.
A large value of nmerge may improve merge performance and decrease temporary storage utilization at the expense of increased memory usage and I/O. Conversely a small value of nmerge may reduce memory requirements and I/O at the expense of temporary storage consumption and merge performance.
The value of nmerge must be at least 2. The default value is currently 16, but this is implementation-dependent and may change in the future.
The value of nmerge may be bounded by a resource limit for open
file descriptors. The commands ‘ulimit -n’ or ‘getconf
OPEN_MAX’ may display limits for your systems; these limits may be
modified further if your program already has some files open, or if
the operating system has other limits on the number of open files. If
the value of nmerge exceeds the resource limit, sort
silently uses a smaller value.
Write output to output-file instead of standard output.
Normally, sort reads all input before opening
output-file, so you can sort a file in place by using
commands like sort -o F F and cat F | sort -o F.
However, it is often safer to output to an otherwise-unused file, as
data may be lost if the system crashes or sort encounters
an I/O or other serious error while a file is being sorted in place.
Also, sort with --merge (-m) can open
the output file before reading all input, so a command like cat
F | sort -m -o F - G is not safe as sort might start
writing F before cat is done reading it.
On newer systems, -o cannot appear after an input file if
POSIXLY_CORRECT is set, e.g., ‘sort F -o F’. Portable
scripts should specify -o output-file before any input
files.
Use file as a source of random data used to determine which random hash function to use with the -R option. See Sources of random data.
Make sort stable by disabling its last-resort comparison.
This option has no effect if no fields or global ordering options
other than --reverse (-r) are specified.
Use a main-memory sort buffer of the given size. By default, size is in units of 1024 bytes. Appending ‘%’ causes size to be interpreted as a percentage of physical memory. Appending ‘K’ multiplies size by 1024 (the default), ‘M’ by 1,048,576, ‘G’ by 1,073,741,824, and so on for ‘T’, ‘P’, ‘E’, ‘Z’, ‘Y’, ‘R’, and ‘Q’. Appending ‘b’ causes size to be interpreted as a byte count, with no multiplication.
This option can improve the performance of sort by causing it
to start with a larger or smaller sort buffer than the default.
However, this option affects only the initial buffer size. The buffer
grows beyond size if sort encounters input lines larger
than size.
Use character separator as the field separator when finding the
sort keys in each line. By default, fields are separated by the empty
string between a non-blank character and a blank character.
By default a blank is a space or a tab, but the LC_CTYPE locale
can change this.
That is, given the input line ‘ foo bar’, sort breaks it
into fields ‘ foo’ and ‘ bar’. The field separator is
not considered to be part of either the field preceding or the field
following, so with ‘sort -t " "’ the same input line has
three fields: an empty field, ‘foo’, and ‘bar’.
However, fields that extend to the end of the line,
as -k 2, or fields consisting of a range, as -k 2,3,
retain the field separators present between the endpoints of the range.
To specify ASCII NUL as the field separator, use the two-character string ‘\0’, e.g., ‘sort -t '\0'’.
Use directory tempdir to store temporary files, overriding the
TMPDIR environment variable. If this option is given more than
once, temporary files are stored in all the directories given. If you
have a large sort or merge that is I/O-bound, you can often improve
performance by using this option to specify directories on different
file systems.
Set the number of sorts run in parallel to n. By default,
n is set to the number of available processors, but limited
to 8, as performance gains diminish after that.
Using n threads increases the memory usage by
a factor of log n. Also see nproc: Print the number of available processors.
Normally, output only the first of a sequence of lines that compare equal. For the --check (-c or -C) option, check that no pair of consecutive lines compares equal.
This option also disables the default last-resort comparison.
The commands sort -u and sort | uniq are equivalent, but
this equivalence does not extend to arbitrary sort options.
For example, sort -n -u inspects only the value of the initial
numeric string when checking for uniqueness, whereas sort -n |
uniq inspects the entire line. See uniq: Uniquify files.
Delimit items with a zero byte rather than a newline (ASCII LF). I.e., treat input as items separated by ASCII NUL and terminate output items with ASCII NUL. This option can be useful in conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which do the same in order to reliably handle arbitrary file names (even those containing blanks or other special characters).
Historical (BSD and System V) implementations of sort have
differed in their interpretation of some options, particularly
-b, -f, and -n.
GNU sort follows the POSIX
behavior, which is usually (but not always!) like the System V behavior.
According to POSIX, -n no longer implies -b. For
consistency, -M has been changed in the same way. This may
affect the meaning of character positions in field specifications in
obscure cases. The only fix is to add an explicit -b.
A position in a sort field specified with -k may have any of the option letters ‘MbdfghinRrV’ appended to it, in which case no global ordering options are inherited by that particular field. The -b option may be independently attached to either or both of the start and end positions of a field specification, and if it is inherited from the global options it will be attached to both. If input lines can contain leading or adjacent blanks and -t is not used, then -k is typically combined with -b or an option that implicitly ignores leading blanks (‘Mghn’) as otherwise the varying numbers of leading blanks in fields can cause confusing results.
If the start position in a sort field specifier falls after the end of the line or after the end field, the field is empty. If the -b option was specified, the ‘.c’ part of a field specification is counted from the first nonblank character of the field.
On systems not conforming to POSIX 1003.1-2001,
sort supports a traditional origin-zero
syntax ‘+pos1 [-pos2]’ for specifying sort keys.
The traditional command ‘sort +a.x -b.y’
is equivalent to ‘sort -k a+1.x+1,b’ if y
is ‘0’ or absent, otherwise it is equivalent to ‘sort -k
a+1.x+1,b+1.y’.
This traditional behavior can be controlled with the
_POSIX2_VERSION environment variable (see Standards conformance); it can also be enabled when POSIXLY_CORRECT is
not set by using the traditional syntax with ‘-pos2’ present.
Scripts intended for use on standard hosts should avoid traditional syntax and should use -k instead. For example, avoid ‘sort +2’, since it might be interpreted as either ‘sort ./+2’ or ‘sort -k 3’. If your script must also run on hosts that support only the traditional syntax, it can use a test like ‘if sort -k 1 </dev/null >/dev/null 2>&1; then …’ to decide which syntax to use.
Here are some examples to illustrate various combinations of options.
sort -n -r
sort --parallel=4 -S 10M
sort -k 3b
sort -t : -k 2,2n -k 5.3,5.4
If you had written -k 2n instead of -k 2,2n
sort would have used all characters beginning in the second field
and extending to the end of the line as the primary numeric
key. For the large majority of applications, treating keys spanning
more than one field as numeric will not do what you expect.
Also, the ‘n’ modifier was applied to the field-end specifier for the first key. It would have been equivalent to specify -k 2n,2 or -k 2n,2n. All modifiers except ‘b’ apply to the associated field, regardless of whether the modifier character is attached to the field-start and/or the field-end part of the key specifier.
sort -t : -k 5b,5 -k 3,3n /etc/passwd sort -t : -n -k 5b,5 -k 3,3 /etc/passwd sort -t : -b -k 5,5 -k 3,3n /etc/passwd
These three commands have equivalent effect. The first specifies that the first key’s start position ignores leading blanks and the second key is sorted numerically. The other two commands rely on global options being inherited by sort keys that lack modifiers. The inheritance works in this case because -k 5b,5b and -k 5b,5 are equivalent, as the location of a field-end lacking a ‘.c’ character position is not affected by whether initial blanks are skipped.
4.150.156.3 - - [01/Apr/2020:06:31:51 +0000] message 1 211.24.3.231 - - [24/Apr/2020:20:17:39 +0000] message 2
Fields are separated by exactly one space. Sort IPv4 addresses lexicographically, e.g., 212.61.52.2 sorts before 212.129.233.201 because 61 is less than 129.
sort -s -t ' ' -k 4.9n -k 4.5M -k 4.2n -k 4.14,4.21 file*.log | sort -s -t '.' -k 1,1n -k 2,2n -k 3,3n -k 4,4n
This example cannot be done with a single POSIX sort invocation,
since IPv4 address components are separated by ‘.’ while dates
come just after a space. So it is broken down into two invocations of
sort: the first sorts by timestamp and the second by IPv4
address. The timestamp is sorted by year, then month, then day, and
finally by hour-minute-second field, using -k to isolate each
field. Except for hour-minute-second there’s no need to specify the
end of each key field, since the ‘n’ and ‘M’ modifiers sort
based on leading prefixes that cannot cross field boundaries. The
IPv4 addresses are sorted lexicographically. The second sort uses
‘-s’ so that ties in the primary key are broken by the secondary
key; the first sort uses ‘-s’ so that the combination of the two
sorts is stable. As a GNU extension, the above example could
be achieved in a single sort invocation by sorting the
IPv4 address field using a ‘V’ version type, like ‘-k1,1V’.
find src -type f -print0 | sort -z -f | xargs -0 etags --append
The use of -print0, -z, and -0 in this case means that file names that contain blanks or other special characters are not broken up by the sort operation.
awk '{print length, $0}' /etc/passwd | sort -n | cut -f2- -d' '
In general this technique can be used to sort data that the sort
command does not support, or is inefficient at, sorting directly.
ls */* | sort -t / -k 1,1R -k 2,2
If you
use a non-POSIX locale (e.g., by setting LC_ALL
to ‘en_US’), then sort may produce output that is sorted
differently than you’re accustomed to. In that case, set the LC_ALL
environment variable to ‘C’. Setting only LC_COLLATE
has two problems. First, it is ineffective if LC_ALL is also set.
Second, it has undefined behavior if LC_CTYPE (or LANG, if
LC_CTYPE is unset) is set to an incompatible value. For example,
you get undefined behavior if LC_CTYPE is ja_JP.PCK but
LC_COLLATE is en_US.UTF-8.