unix 下的C开发手册,还用详细的例程。

																				head																The Single UNIX ® Specification, Version 2				Copyright © 1997 The Open Group												 NAME				head - copy the first part of files				 SYNOPSIS												head [-n number][file...]								head [number][file...]												 DESCRIPTION				The				head				utility will copy its input files to the standard output,				ending the output for each file at a designated point.								Copying will end at the point in each input file indicated by the				-n number				option				(or the				-number				argument).				The option-argument				number				will be counted in units of lines.				 OPTIONS				The				head				utility supports the XBD specification, Utility Syntax Guidelines  ,				except that the obsolescent version accepts multi-character numeric options.								The following options are supported:												-n number								The first				number				lines of each input file will be copied to				standard output.				The				number				option-argument must be a positive decimal integer.								-number				The				number				argument is a positive decimal integer with the				same effect as the -n number option.																If no options are specified,				head				will act as if				-n 10				had been specified.				 OPERANDS				The following operand is supported:												fileA pathname of an input file.				If no				file				operands are specified,				the standard input will be used.												 STDIN				The standard input will be used only if no				file				operands are specified.				See the INPUT FILES section.				 INPUT FILES				Input files must be text files, but the line length				is not restricted to				{LINE_MAX}				bytes.				 ENVIRONMENT VARIABLES				The following environment variables affect the execution of				head:												LANGProvide a default value for the internationalisation variables				that are unset or null.				If				LANG				is unset or null, the corresponding value from the				implementation-dependent default locale will be used.				If any of the internationalisation variables contains an invalid setting, the				utility will behave as if none of the variables had been defined.								LC_ALL				If set to a non-empty string value,				override the values of all the other internationalisation variables.								LC_CTYPE				Determine the				locale for the interpretation of sequences of bytes of text data as				characters (for example, single- as opposed to multi-byte characters				in arguments and input files).												LC_MESSAGES				Determine the locale that should be used to affect				the format and contents of diagnostic				messages written to standard error.								NLSPATH				Determine the location of message catalogues				for the processing of				LC_MESSAGES .												 ASYNCHRONOUS EVENTS				Default.				 STDOUT				The standard output will contain				designated portions of the input files.								If multiple				file				operands are specified,				head				will precede the output for each with the header:								"\n==> %s <==\n", <pathname>								except that the first header written will not include the initial				newline character.				 STDERR				Used only for diagnostic messages.				 OUTPUT FILES				None.				 EXTENDED DESCRIPTION				None.				 EXIT STATUS				The following exit values are returned:												0Successful completion.								>0An error occurred.												 CONSEQUENCES OF ERRORS				Default.				 APPLICATION USAGE				None.				 EXAMPLES				To write the first ten lines of all files				(except those with a leading period)				in the directory:												head *												 FUTURE DIRECTIONS				The obsolescent				-number				form may be withdrawn in a future issue.				Applications should use the				-n number				option.				 SEE ALSO				sed,				tail.												UNIX ® is a registered Trademark of The Open Group.				Copyright © 1997 The Open Group				 [ Main Index | XSH | XCU | XBD | XCURSES | XNS ]