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System Services

The following macros check for operating system services or capabilities.

AC_PATH_X Macro
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.

AC_PATH_XTRA Macro
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.

AC_SYS_INTERPRETER Macro
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.

AC_SYS_LARGEFILE Macro
Arrange for large-file support. 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).

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

AC_SYS_POSIX_TERMIOS Macro
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.