comm [-123] file1 file2
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.
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:
The following operands shall be supported:
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.
The standard input shall be used only if one of the file1 or file2 operands refers to standard input. See the INPUT FILES section.
The input files shall be text files.
The following environment variables shall affect the execution of comm:
Determine the locale for the collating sequence comm expects to have been used when the input files were sorted.
Default.
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:
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:
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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
Default.
The following sections are informative.
If the input files are not properly presorted, the output of comm might not be useful.
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.
None.
None.
cmp , diff , sort , uniq