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Linux 2.6 - man page for sort (linux section 1posix)

SORT(P) 			    POSIX Programmer's Manual				  SORT(P)

       sort - sort, merge, or sequence check text files

       sort [-m][-o output][-bdfinru][-t char][-k keydef]... [file...]

       sort -c [-bdfinru][-t char][-k keydef][file]

       The sort utility shall perform one of the following functions:

	1. Sort  lines of all the named files together and write the result to the specified out-

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

	3. 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.

       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  follow  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 ordering  rules.  When	ordering  options
       appear  independent  of	any  key field specifications, the requested field ordering 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 characters, according to the current
	      setting of LC_CTYPE , shall be significant in comparisons. The  behavior	is  unde-
	      fined 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 equivalent for	the  purposes  of

       -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 char-
	      acter 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.  Lead-
	      ing 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  inde-
	      pendently 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 separa-

       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:


       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 modi-
       fiers  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 speci-
       fied, 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 otherwise 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

       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.

       The standard input shall be used only if no file operands are specified, or if a file  op-
       erand is '-' .  See the INPUT FILES section.

       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.

       The following environment variables shall affect the execution of sort:

       LANG   Provide a default value for the internationalization variables that  are	unset  or
	      null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
	      nationalization Variables for the precedence of internationalization variables used
	      to determine the values of locale categories.)

       LC_ALL If  set  to a non-empty string value, override the values of all the other interna-
	      tionalization variables.


	      Determine the locale for ordering rules.

	      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 argu-
	      ments and input files) and the behavior of character classification for the -b, -d,
	      -f, -i, and -n options.

	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.


	      Determine the locale for the definition of the radix character and thousands  sepa-
	      rator for the -n option.

	      Determine the location of message catalogs for the processing of LC_MESSAGES .


       Unless  the  -o	or -c options are in effect, the standard output shall contain the sorted

       The standard error shall be used for diagnostic messages. A warning message about correct-
       ing  an	incomplete  last  line of an input file may be generated, but need not affect the
       final exit status.

       If the -o option is in effect, the sorted input shall be written to the file output.

       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 preceding field separator.

       The field_start portion of the keydef option-argument shall have the form:


       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:


       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  omit-
       ted, 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, characters within a field shall be
       counted from the first non-  <blank>  in  the  field.  (This  shall  apply  separately  to
       first_character and last_character.)

       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.


       The following sections are informative.

       The  default  value  for  -t,  <blank>,	has  different	properties  from, for example, -t
       "<space>". If a line contains:


       the following treatment would occur with default separation  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 exam-
       ple, this command returns an exit status of zero, meaning the input was already sorted:

	      sort -c -k 2 <<eof

       (assuming that a <tab> precedes the <space> in the current 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
	      Columbia|100385|South Carolina

       where the second field can be correctly sorted numerically  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 map-
       ping between an uppercase and a lowercase letter.

	1. The following command sorts the contents of infile with the second field as	the  sort

	   sort -k 2,2 infile

	2. The	following  command  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 sepa-

	   sort -r -o outfile -k 2.2,2.2 infile1 infile2

	3. 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

	4. 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

	5. 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

       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  imple-
       mentation artifact and was not standardized.

       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 documentation appeared to require implementations to determine
       the proper buffer length during the sort phase of operation, 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 implementations. It is used to specify a direc-
       tory for intermediate 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 consistent 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
       offset 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 recommen-
       dation 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 wishing to achieve the previ-
       ously mentioned side effects has to code the -b flag explicitly.


       comm , join , uniq , the System Interfaces volume of IEEE Std 1003.1-2001, toupper()

       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  SORT(P)

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