Provided by: manpages-posix_2.16-1_all bug

NAME

       comm - select or reject lines common to two files

SYNOPSIS

       comm [-123] file1 file2

DESCRIPTION

       The  comm  utility  shall  read  file1  and  file2, which should be ordered in the current
       collating sequence, and produce three text columns as output: lines only in  file1,  lines
       only in file2, and lines in both files.

       If  the  lines  in  both  files are not ordered according to the collating sequence of the
       current locale, the results are unspecified.

OPTIONS

       The comm utility shall conform to the Base  Definitions  volume  of  IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -1     Suppress the output column of lines unique to file1.

       -2     Suppress the output column of lines unique to file2.

       -3     Suppress the output column of lines duplicated in file1 and file2.

OPERANDS

       The following operands shall be supported:

       file1  A  pathname  of the first file to be compared. If file1 is '-' , the standard input
              shall be used.

       file2  A pathname of the second file to be compared. If file2 is '-' , the standard  input
              shall be used.

       If  both  file1  and  file2  refer  to  standard  input or to the same FIFO special, block
       special, or character special file, the results are undefined.

STDIN

       The standard input shall be used only if one of the file1  or  file2  operands  refers  to
       standard input. See the INPUT FILES section.

INPUT FILES

       The input files shall be text files.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of comm:

       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,
              Internationalization 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
              internationalization variables.

       LC_COLLATE

              Determine the locale for the collating sequence comm expects to have been used when
              the input files were sorted.

       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).

       LC_MESSAGES
              Determine the locale that should be used to  affect  the  format  and  contents  of
              diagnostic messages written to standard error.

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

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       The  comm  utility  shall produce output depending on the options selected. If the -1, -2,
       and -3 options are all selected, comm shall write nothing to standard output.

       If the -1 option is not selected, lines contained only in file1 shall be written using the
       format:

              "%s\n", <line in file1>

       If  the  -2  option  is  not selected, lines contained only in file2 are written using the
       format:

              "%s%s\n", <lead>, <line in file2>

       where the string <lead> is as follows:

       <tab>  The -1 option is not selected.

       null string
              The -1 option is selected.

       If the -3 option is not selected, lines contained in both files shall be written using the
       format:

              "%s%s\n", <lead>, <line in both>

       where the string <lead> is as follows:

       <tab><tab>
              Neither the -1 nor the -2 option is selected.

       <tab>  Exactly one of the -1 and -2 options is selected.

       null string
              Both the -1 and -2 options are selected.

       If the input files were ordered according to the collating sequence of the current locale,
       the lines written shall be in the collating sequence of the original lines.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0     All input files were successfully output as specified.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       If the input files are not properly presorted, the output of comm might not be useful.

EXAMPLES

       If a file  named  xcu  contains  a  sorted  list  of  the  utilities  in  this  volume  of
       IEEE Std 1003.1-2001,  a file named xpg3 contains a sorted list of the utilities specified
       in the X/Open Portability Guide, Issue 3, and a file named svid89 contains a  sorted  list
       of the utilities in the System V Interface Definition Third Edition:

              comm -23 xcu xpg3 | comm -23 - svid89

       would  print  a  list of utilities in this volume of IEEE Std 1003.1-2001 not specified by
       either of the other documents:

              comm -12 xcu xpg3 | comm -12 - svid89

       would print a list of utilities specified by all three documents, and:

              comm -12 xpg3 svid89 | comm -23 - xcu

       would print a list of utilities specified by both XPG3 and the SVID, but not specified  in
       this volume of IEEE Std 1003.1-2001.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       cmp , diff , sort , uniq

COPYRIGHT

       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
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .