head(1) General Commands Manual head(1)NAME
head - give first few lines
SYNOPSIS
count] [file ...]
Obsolescent:
[file ...]
DESCRIPTION
prints on standard output the first count lines of each of the specified files, or of the standard input. If count is omitted it defaults
to 10.
If multiple files are specified, outputs before each file a line of this form:
file
Options
The quantity of output is measured in bytes.
The number of units of output.
This option is provided for backward compatibility (see below) and is mutually exclusive of all other options.
The quantity of output is measured in lines; this is the default.
The number of lines (default) or bytes output.
count is an unsigned decimal integer. If (or is not given, the default quantity is 10. This option provides the same func-
tionality as the option, but in a more standard way. Use of the option is recommended where portability between systems is
important.
EXTERNAL INFLUENCES
Environment Variables
determines the interpretation of text within file as single and/or multi-byte characters.
determines the language in which messages are displayed.
If or is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty
variable. If is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of
If any internationalization variable contains an invalid setting, behaves as if all internationalization variables are set to "C". See
environ(5).
International Code Set Support
Single- and multi-byte character code sets are supported.
WARNINGS
The length of the input lines is limited to bytes.
SEE ALSO tail(1), cat(1), more(1), pg(1).
STANDARDS CONFORMANCE head(1)
Check Out this Related Man Page
tail(1) General Commands Manual tail(1)NAME
tail - deliver the last part of a file
SYNOPSIS
number] [file]
number] [file]
number] [file]
Obsolescent:
[file]
DESCRIPTION
copies the named file to the standard output beginning at a designated place. If no file is named, standard input is used.
Command Forms
can be used in three forms as indicated above:
Copy file starting at number blocks from end or beginning of file.
Copy file starting at number bytes from end or beginning of file.
Copy file starting at number lines from end or beginning of file.
with no options specified is equivalent to
Options and Command-Line Arguments
recognizes the following options and command-line arguments:
Follow option. If the input file is a regular file or if file specifies a FIFO, do not terminate after the last line of the input
file has been copied, but read and copy further bytes from the input file when they become available enters an end-
less loop wherein it sleeps for one second then attempts to read and copy further records from the input file). This
is useful when monitoring text being written to a file by another process. If no file argument is specified and the
input is a pipe (FIFO), the option is ignored.
number Decimal integer indicating quantity of output to be copied, measured in units specified by accompanying option. If
number is preceded by a character, copy operation starts number units from beginning of file. If number is preceded
by a character or the option name, copy operation starts number units from end of file. If number is not preceded by
a or option, is assumed. If both the option and number are not specified, is assumed.
Copy file beginning
number 512-byte blocks from end or beginning of file. If number is not specified, is assumed. See number descrip-
tion above.
Copy file beginning
number bytes from end or beginning of file. If number is not specified, is assumed. See number description above.
Copy file beginning
number lines from end or beginning of file. If number is not specified, is assumed. See number description above.
file Name of file to be copied. If not specified, the standard input is used.
If the option is specified, the input file can contain arbitrary data. Otherwise, the input file should be a text file.
Obsolescent Form
In the obsolescent form, option letters can be concatenated after the number argument to select blocks, bytes, or lines. If this syntax is
used, must be the first argument given. If number is not specified, -10 is assumed. This version is provided for backward compatibility
only. The forms discussed previously are recommended for portability.
EXTERNAL INFLUENCES
Environment Variables
determines the locale for the interpretation of sequences of bytes of text data as characters (e.g., single- versus multibyte characters in
arguments and input files).
determines the language in which messages are displayed.
If or is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty
variable. If is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of
If any internationalization variable contains an invalid setting, behaves as if all internationalization variables are set to "C". See
environ(5).
International Code Set Support
Single- and multi-byte character code sets are supported. However, the and options can break multi-byte characters and should be used with
caution in a multi-byte locale environment.
EXAMPLES
Print the last three lines in file to the standard output, and leave in ``follow'' mode:
Print the last 15 bytes of file followed by any lines that are appended to after is initiated until it is killed:
Three ways to print an entire file:
WARNINGS
Various kinds of anomalous behavior may occur with character special files. For piped output, is limited in its output and depends on
process limits.
SEE ALSO dd(1), head(1).
STANDARDS CONFORMANCE tail(1)