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comm(1) General Commands Manual comm(1) NAME comm - Compares two sorted files. SYNOPSIS comm [-123] file1 file2 OPTIONS Suppresses output of the first column (lines in file1 only). Sup- presses output of the second column (lines in file2 only). Suppresses output of the third column (lines common to file1 and file2). The command comm -123 produces no output. DESCRIPTION The comm command reads file1 and file2 and writes three columns to standard output, showing which lines are common to the files and which are unique to each. The leftmost column of standard output includes lines that are in file1 only. The middle column includes lines that are in file2 only. The rightmost column includes lines that are in both file1 and file2. If you specify a hyphen (-) in place of one of the file names, comm reads standard input. Generally, file1 and file2 are sorted according to the collating se- quence specified by the LC_COLLATE environment variable. (See sort(1).) EXIT STATUS Successful completion. Error occurred. EXAMPLES In the following examples, file1 contains the following sorted list of North American cities: Anaheim Baltimore Boston Chicago Cleveland Dallas Detroit Kansas City Milwaukee Minneapolis New York Oakland Seattle Toronto The second file, file2, contains this sorted list: Atlanta Chicago Cincinnati Houston Los Angeles Montreal New York Philadelphia Pittsburgh San Diego San Francisco St. Louis To display the lines unique to each file and common to the two files, enter: comm file1 file2 This command results in the following output: Anaheim At- lanta Baltimore Boston Chicago Cincinnati Cleve- land Dallas Detroit Houston Kansas City Los Angeles Milwaukee Minneapolis Montreal New York Oakland Philadelphia Pittsburgh San Diego San Fran- cisco Seattle St. Louis Toronto The leftmost column contains lines in file1 only, the middle column contains lines in file2 only, and the rightmost column contains lines common to both files. To display any one or two of the three output columns, include the appropriate flags to suppress the columns you do not want. For example, the follow- ing command displays columns 1 and 2 only: comm -3 file1 file2 Anaheim Atlanta Baltimore Boston Cincinnati Cleveland Dallas Detroit Houston Kansas City Los Angeles Milwaukee Minneapolis Montreal Oakland Philadelphia Pittsburgh San Diego San Francisco Seattle St. Louis Toronto The following command displays output from only the second col- umn: comm -13 file1 file2 Atlanta Cincinnati Houston Los Angeles Montreal Philadelphia Pittsburgh San Diego San Francisco St. Louis The following command displays output from only the third col- umn: comm -12 file1 file2 Chicago New York SEE ALSO Commands: cmp(1), diff(1), sdiff(1), sort(1), uniq(1) comm(1)