(autoconf.info)System Services


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5.11 System Services
====================

The following macros check for operating system services or
capabilities.

 -- Macro: AC_PATH_X
     Try to locate the X Window System include files and libraries.  If
     the user gave the command line options `--x-includes=DIR' and
     `--x-libraries=DIR', use those directories.

     If either or both were not given, get the missing values by running
     `xmkmf' (or an executable pointed to by the `XMKMF' environment
     variable) on a trivial `Imakefile' and examining the makefile that
     it produces.  Setting `XMKMF' to `false' disables this method.

     If this method fails to find the X Window System, `configure'
     looks for the files in several directories where they often reside.
     If either method is successful, set the shell variables
     `x_includes' and `x_libraries' to their locations, unless they are
     in directories the compiler searches by default.

     If both methods fail, or the user gave the command line option
     `--without-x', set the shell variable `no_x' to `yes'; otherwise
     set it to the empty string.

 -- Macro: AC_PATH_XTRA
     An enhanced version of `AC_PATH_X'.  It adds the C compiler flags
     that X needs to output variable `X_CFLAGS', and the X linker flags
     to `X_LIBS'.  Define `X_DISPLAY_MISSING' if X is not available.

     This macro also checks for special libraries that some systems
     need in order to compile X programs.  It adds any that the system
     needs to output variable `X_EXTRA_LIBS'.  And it checks for
     special X11R6 libraries that need to be linked with before
     `-lX11', and adds any found to the output variable `X_PRE_LIBS'.


 -- Macro: AC_SYS_INTERPRETER
     Check whether the system supports starting scripts with a line of
     the form `#!/bin/sh' to select the interpreter to use for the
     script.  After running this macro, shell code in `configure.ac'
     can check the shell variable `interpval'; it is set to `yes' if
     the system supports `#!', `no' if not.

 -- Macro: AC_SYS_LARGEFILE
     Arrange for large-file support
     (http://www.unix-systems.org/version2/whatsnew/lfs20mar.html).  On
     some hosts, one must use special compiler options to build
     programs that can access large files.  Append any such options to
     the output variable `CC'.  Define `_FILE_OFFSET_BITS' and
     `_LARGE_FILES' if necessary.

     Large-file support can be disabled by configuring with the
     `--disable-largefile' option.

     If you use this macro, check that your program works even when
     `off_t' is wider than `long int', since this is common when
     large-file support is enabled.  For example, it is not correct to
     print an arbitrary `off_t' value `X' with `printf ("%ld", (long
     int) X)'.

     The LFS introduced the `fseeko' and `ftello' functions to replace
     their C counterparts `fseek' and `ftell' that do not use `off_t'.
     Take care to use `AC_FUNC_FSEEKO' to make their prototypes
     available when using them and large-file support is enabled.

 -- Macro: AC_SYS_LONG_FILE_NAMES
     If the system supports file names longer than 14 characters, define
     `HAVE_LONG_FILE_NAMES'.

 -- Macro: AC_SYS_POSIX_TERMIOS
     Check to see if the Posix termios headers and functions are
     available on the system.  If so, set the shell variable
     `ac_cv_sys_posix_termios' to `yes'.  If not, set the variable to
     `no'.


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