head

The head utility shall copy its input files to the standard output, ending the output for each file at a designated point. 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. The standard input shall be used if no file operands are specified, and shall be used if a file operand is '-' and the implementation treats the '-' as meaning standard input. Otherwise, the standard input shall not be used. See the INPUT FILES section. Input files shall be text files, but the line length is not restricted to {LINE MAX} bytes. Provide a default value for the internationalization variables that are unset or null. (See XBD 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. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( except that the first header written shall not include the initial . Although it is possible to simulate head with sed 10q for a single file, the standard developers decided that the popularity of head on historical BSD systems warranted its inclusion alongside tail . POSIX.1-2017 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.1-2017 but may be present in some implementations. The normative text is reworded to avoid use of the term "must" for application requirements. The DESCRIPTION is updated to clarify that when a file contains less than the number of lines requested, the entire file is copied to standard output. The APPLICATION USAGE section is removed and the EXAMPLES section is corrected.