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cat(1) General Commands Manual cat(1) NAME cat - Concatenates or displays files SYNOPSIS cat [-benrstuv] file...|- The cat command reads each specified file in sequence and writes it to standard output. STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: cat: XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. OPTIONS [DIGITAL] Omits line numbers from blank lines when -n is specified. If you specify the -b option, the -n option is automatically invoked with it. [DIGITAL] Same as the -v option with a $ (dollar sign) character displayed at the end of each line. [DIGITAL] Displays output lines preceded by line numbers, numbered sequentially from 1. [DIGITAL] Re- places multiple consecutive empty lines with one empty line, so that there is never more than one empty line between lines containing char- acters. [DIGITAL] Does not display a message if cat cannot find an input file. (Silent option.) [DIGITAL] Same as the -v option, with the tab character printed as <Ctrl-i> (^I). Does not buffer output. Writes bytes from the input file to standard output without delay as each is read. [DIGITAL] Displays nonprinting characters so that they are visible. OPERANDS The name of the file to be displayed. If you do not specify a file or if you specify - (dash) instead of file, cat reads from standard input. The cat command accepts multiple occurrences of - (dash) as a file argument. DESCRIPTION [DIGITAL] The cat command is frequently used with > (redirection sym- bol) to concatenate the specified files and write them to the specified destination. (See CAUTIONS.) The cat command is also used with >> to append a file to another file. CAUTIONS Do not redirect output to one of the input files using the > (redirec- tion symbol). If you do this, you lose the original data in the input file because the shell truncates it before cat can read it. (See also the sh command.) EXIT STATUS The following exit values are returned: Successful completion. An er- ror occurred. EXAMPLES To display the file notes, enter: cat notes If the file is longer than one screenful, it scrolls by too quickly to read. To display a file one page at a time, use the more command. To concatenate several files, enter: cat sec- tion1.1 section1.2 section1.3 > section1 This creates a file named section1 that is a copy of section1.1 followed by section1.2 and section1.3. To suppress error mes- sages about files that do not exist, enter: cat -s section2.1 section2.2 section2.3 > section2 If section2.1 does not exist, this command concatenates sec- tion2.2 and section2.3. Note that the message goes to standard error, so it does not appear in the output file. The result is the same if you do not use the -s option, except that cat dis- plays the error message: cat: cannot open section2.1 You may want to suppress this message with the -s option when you use the cat command in shell procedures. To append one file to the end of another, enter: cat section1.4 >> section1 The >> in this command specifies that a copy of section1.4 be added to the end of section1. If you want to replace the file, use a single > symbol. To add text to the end of a file, enter: cat >> notes Get milk on the way home <Ctrl-d> Get milk on the way home is added to the end of notes. With this syntax, the cat command does not display a prompt; it waits for you to enter text. Press the End-of-File key sequence (<Ctrl-d> above) to indicate you are finished. To concatenate several files with text entered from the keyboard, enter: cat section3.1 - section3.3 > section3 This concatenates section3.1, text from the keyboard, and sec- tion3.3 to create the file section3. To concatenate several files with output from another command, enter: ls | cat sec- tion4.1 - > section4 This copies section4.1, and then the output of the ls command to the file section4. To get two pieces of input from the terminal (when standard input is a terminal) with a single command invo- cation, enter: cat start - middle - end > file1 If standard input is a regular file, however, the preceding com- mand is equivalent to the following: cat start - middle /dev/null end > file1 This is because the entire contents of the file would be con- sumed by cat the first time it saw - (dash) as a file argument. An End-of-File condition would then be detected immediately when - (dash) appeared the second time. ENVIRONMENT VARIABLES The following environment variables affect the execution of cat: Pro- vides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization vari- ables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, over- rides the values of all the other internationalization variables. De- termines 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). Determines the locale for the format and contents of diagnostic messages written to standard error. Deter- mines the location of message catalogues for the processing of LC_MES- SAGES. SEE ALSO Commands: more(1), ksh(1), pack(1), pg(1), pr(1), Bourne shell sh(1b), POSIX shell sh(1p) Standards: standards(5) cat(1)