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comm(C)

comm -- select or reject lines common to two sorted files

Syntax

comm [ -123 ] file1 file2

Description

comm reads file1 and file2, which should be ordered according to the collating sequence defined by the current locale (see sort(C)), and produces a three-column output: lines only in file1; lines only in file2; and lines in both files. The filename ``-'' means the standard input.

Flags 1, 2, or 3 suppress printing of the corresponding column. Thus comm -12 prints only the lines common to the two files; comm -23 prints only lines in the first file but not in the second; comm -123 is a no-op (does nothing).

comm understands the -- option delimiter.

Exit values

comm returns the following values:

0
all input files were successfully output as specified

>0
an error occurred

See also

cmp(C), diff(C), sort(C), uniq(C)

Standards conformance

comm is conformant with:

ISO/IEC DIS 9945-2:1992, Information technology - Portable Operating System Interface (POSIX) - Part 2: Shell and Utilities (IEEE Std 1003.2-1992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992.

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