PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

COMM(1P)                  POSIX Programmer's Manual                 COMM(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       comm — select or reject lines common to two files

SYNOPSIS         top

       comm [−123] file1 file2

DESCRIPTION         top

       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         top

       The comm utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, 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         top

       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         top

       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         top

       The input files shall be text files.

ENVIRONMENT VARIABLES         top

       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 POSIX.1‐2008, 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         top

       Default.

STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    All input files were successfully output as specified.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

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

EXAMPLES         top

       If a file named xcu contains a sorted list of the utilities in this
       volume of POSIX.1‐2008, 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 POSIX.1‐2008 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 POSIX.1‐2008.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       cmp(1p), diff(1p), sort(1p), uniq(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            COMM(1P)

Pages that refer to this page: cmp(1p)diff(1p)join(1p)sort(1p)uniq(1p)