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94 lines
3.2 KiB
Text
94 lines
3.2 KiB
Text
@c -*-texinfo-*-
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@c This is part of the GNU Guile Reference Manual.
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@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004
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@c Free Software Foundation, Inc.
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@c See the file guile.texi for copying conditions.
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@page
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@node Command Line Handling
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@section Handling Command Line Options and Arguments
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@c This chapter was written and contributed by Martin Grabmueller.
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The ability to accept and handle command line arguments is very
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important when writing Guile scripts to solve particular problems, such
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as extracting information from text files or interfacing with existing
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command line applications. This chapter describes how Guile makes
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command line arguments available to a Guile script, and the utilities
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that Guile provides to help with the processing of command line
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arguments.
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When a Guile script is invoked, Guile makes the command line arguments
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accessible via the procedure @code{command-line}, which returns the
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arguments as a list of strings.
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For example, if the script
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@example
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#! /usr/local/bin/guile -s
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!#
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(write (command-line))
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(newline)
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@end example
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@noindent
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is saved in a file @file{cmdline-test.scm} and invoked using the command
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line @code{./cmdline-test.scm bar.txt -o foo -frumple grob}, the output
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is
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@example
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("./cmdline-test.scm" "bar.txt" "-o" "foo" "-frumple" "grob")
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@end example
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If the script invocation includes a @code{-e} option, specifying a
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procedure to call after loading the script, Guile will call that
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procedure with @code{(command-line)} as its argument. So a script that
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uses @code{-e} doesn't need to refer explicitly to @code{command-line}
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in its code. For example, the script above would have identical
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behaviour if it was written instead like this:
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@example
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#! /usr/local/bin/guile \
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-e main -s
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!#
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(define (main args)
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(write args)
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(newline))
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@end example
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(Note the use of the meta switch @code{\} so that the script invocation
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can include more than one Guile option: @xref{The Meta Switch}.)
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These scripts use the @code{#!} POSIX convention so that they can be
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executed using their own file names directly, as in the example command
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line @code{./cmdline-test.scm bar.txt -o foo -frumple grob}. But they
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can also be executed by typing out the implied Guile command line in
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full, as in:
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@example
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$ guile -s ./cmdline-test.scm bar.txt -o foo -frumple grob
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@end example
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@noindent
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or
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@example
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$ guile -e main -s ./cmdline-test2.scm bar.txt -o foo -frumple grob
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@end example
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Even when a script is invoked using this longer form, the arguments that
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the script receives are the same as if it had been invoked using the
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short form. Guile ensures that the @code{(command-line)} or @code{-e}
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arguments are independent of how the script is invoked, by stripping off
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the arguments that Guile itself processes.
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A script is free to parse and handle its command line arguments in any
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way that it chooses. Where the set of possible options and arguments is
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complex, however, it can get tricky to extract all the options, check
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the validity of given arguments, and so on. This task can be greatly
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simplified by taking advantage of the module @code{(ice-9 getopt-long)},
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which is distributed with Guile, @xref{getopt-long}.
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@c Local Variables:
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@c TeX-master: "guile.texi"
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@c End:
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