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(autoconf.info)System Services

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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' on a
     trivial `Imakefile' and examining the `Makefile' that it produces.
     If that fails (such as if `xmkmf' is not present), look for them
     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/csh' 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 will be set to `yes'
     if the system supports `#!', `no' if not.

 - Macro: AC_SYS_LARGEFILE
     Arrange for large-file support(1).  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 longer than `long', 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)
     X)'.

 - 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 POSIX termios headers and functions are available
     on the system.  If so, set the shell variable
     `am_cv_sys_posix_termios' to `yes'.  If not, set the variable to
     `no'.

   ---------- Footnotes ----------

   (1) large-file support,
<http://www.sas.com/standards/large.file/x_open.20Mar96.html>.