cat - Concatenates or displays files
cat [-benrstuv] file... | -
The cat command reads each specified file in sequence and
writes it to standard output.
Interfaces documented on this reference page conform to
industry standards as follows:
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
[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 <Ctrli>
(^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.
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.
[Tru64 UNIX] The cat command is frequently used with >
(redirection symbol) 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.
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.)
The following exit values are returned: Successful completion.
An error occurred.
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 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 - >
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 [Toc] [Back]
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 variables 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
format and contents of diagnostic messages written to
standard error. Determines the location of message catalogues
for the processing of LC_MESSAGES.
Commands: more(1), ksh(1), pack(1), pg(1), pr(1), Bourne
shell sh(1b), POSIX shell sh(1p)
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