|HEAD(1P)||POSIX Programmer's Manual||HEAD(1P)|
head [-n number] [file...]
Copying shall end at the point in each input file indicated by the -n number option. The option-argument number shall be counted in units of lines.
The following option shall be supported:
- -n number
- The first number lines of each input file shall be copied to standard output. The application shall ensure that the number option-argument is a positive decimal integer.
When a file contains less than number lines, it shall be copied to standard output in its entirety. This shall not be an error.
If no options are specified, head shall act as if -n 10 had been specified.
- A pathname of an input file. If no file operands are specified, the standard input shall be used.
- Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1‐2017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
- If set to a non-empty string value, override the values of all the other internationalization variables.
- Determine 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 and input files).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
- Determine the location of message catalogs for the processing of LC_MESSAGES.
If multiple file operands are specified, head shall precede the output for each with the header:
"\n==> %s <==\n", <pathname>
except that the first header written shall not include the initial <newline>.
- Successful completion.
- An error occurred.
The following sections are informative.
head -- *
POSIX.1‐2008 version of head follows the Utility Syntax Guidelines. The -n option was added to this new interface so that head and tail would be more logically related. Earlier versions of this standard allowed a -number option. This form is no longer specified by POSIX.1‐2008 but may be present in some implementations.
There is no -c option (as there is in tail) because it is not historical practice and because other utilities in this volume of POSIX.1‐2017 provide similar functionality.
The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
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|2017||IEEE/The Open Group|