aclocal command in Linux with Examples

aclocal command in Linux is used to automatically generate 'aclocal.m4' files from configure.in file. automake in Linux contain a lot of autoconf macros that can be used in the different packages. These macros must be defined in the aclocal.m4. If not, then it can’t be accessed by the autoconf.

The aclocal command first scans for macro definitions in the .m4 files in its default directory ('/usr/share/aclocal' on some systems) and also in the file acinclude.m4 after which it scans for macros used in the configure.in file. It will generate an aclocal.m4 file that contains definitions of all the m4 macros required by autoconf.

Syntax

aclocal [, OPTION/]... [, SRCDIR/]

where,

• [OPTION]: Specifies various options to control the behavior of the aclocal command.
• [SRCDIR]: The source directory containing the configure.in or configure.ac file.

Common Options for 'aclocal' command

1. --help:

Display the help message and then exits.

2. --verbose:

It prints the names of the files it examines.

3. --version:

Shows the version number and then exits.

4. -W or --warnings:

Reports the warning's falling in the category. The warning categories are:

Other important Options that can be used are:

• --acdir=dir: This option is used to search macro files in directory dir instead of the default directory.
• --print-ac-dir: Prints the name of the directory to be searched for m4 files, then exit.
• --force: Always updates the output file.
• --dry-run: Pretends to update the files.
• -I DIRECTORY: Add the directory DIR to the list of directories searched for the .m4 files.
• --system-acdir=dir: Shows the directory holding third party system wide files.
• --output=FILE: Cause the output to be put into specified FILE instead of aclocal.m4.
• --diff: Runs the command diff on m4 files that might be changed.

Conclusion

The aclocal command is a vital tool for anyone working with the GNU Autotools suite to build and package software on Linux. By automating the generation of the aclocal.m4 file, it simplifies the process of managing macros needed for autoconf. aclocal ensures that your software package is ready to compile and build smoothly.