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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
-b [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.
-e [Tru64 UNIX] Same as the -v option with a $ (dollar sign) character
displayed at the end of each line.
-n [Tru64 UNIX] Displays output lines preceded by line numbers, numbered
sequentially from 1.
-r [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.
-s [Tru64 UNIX] Does not display a message if cat cannot find an input
file. (Silent option.)
-t [Tru64 UNIX] Same as the -v option, with the tab character printed as
<Ctrl-i> (^I).
-u Does not buffer output. Writes bytes from the input file to standard
output without delay as each is read.
-v [Tru64 UNIX] Displays nonprinting characters so that they are visible.
OPERANDS
file
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
[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.
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:
0 Successful completion.
>0 An error occurred.
EXAMPLES
1. 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.
2. 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.
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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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:
LANG
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.
LC_ALL
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
LC_CTYPE
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).
LC_MESSAGES
Determines the locale for the format and contents of diagnostic
messages written to standard error.
NLSPATH
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)
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Index for
Section 1 |
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Alphabetical
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Top of
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