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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 standards as follows: cat: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
[Tru64 UNIX] Omits line numbers from blank lines when -n is specified. If you specify the -b option, the -n option is automatically invoked with it. [Tru64 UNIX] Same as the -v option with a $ (dollar sign) character displayed at the end of each line. [Tru64 UNIX] Displays output lines preceded by line numbers, numbered sequentially from 1. [Tru64 UNIX] Replaces multiple consecutive empty lines with one empty line, so that there is never more than one empty line between lines containing characters. [Tru64 UNIX] Does not display a message if cat cannot find an input file. (Silent option.) [Tru64 UNIX] 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. [Tru64 UNIX] 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 mul- tiple occurrences of - (dash) as a file argument. DESCRIPTION
[Tru64 UNIX] The cat command is frequently used with > (redirection symbol) to concatenate the specified files and write them to the spec- ified 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 > (redirection 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 error 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 com- mand. To concatenate several files, enter: cat section1.1 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 messages 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 section2.2 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 displays 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 section3.3 to create the file section3. To concatenate several files with output from another command, enter: ls | cat section4.1 - > 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 invocation, enter: cat start - middle - end > file1 If standard input is a regular file, however, the preceding command is equivalent to the following: cat start - middle /dev/null end > file1 This is because the entire contents of the file would be consumed 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: Provides 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, overrides the values of all the other internationalization variables. Determines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multibyte characters in arguments). Determines the locale for the for- mat and contents of diagnostic messages written to standard error. Determines the location of message catalogues for the processing of LC_MESSAGES. 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)
