Wordsplit - an enhanced word splitter

Table of Contents

1 Overview

This package provides a set of C functions for parsing input strings. Default parsing rules are are similar to those used in Bourne shell. This includes tilde expansion, variable expansion, quote removal, word splitting, command substitution, and path expansion. Parsing is controlled by a number of settings which allow the caller to alter processing at each of these phases or even to disable any of them. Thus, wordsplit can be used for parsing inputs in different formats, from simple character-delimited entries, as in /etc/passwd, and up to complex shell statements.

The following code fragment shows the basic usage:

/* This variable controls parsing */
wordsplit_t ws;
int rc;

/* Provide variable definitions */
ws.ws_env = (const char **) environ;
/* Provide a function for expanding commands */
ws.ws_command = runcom;
/* Split input_string into words */
rc = wordsplit(input_string, &ws,
               WRDSF_QUOTE     /* Handle both single and double quoted strings as words. */
               | WRDSF_SQUEEZE_DELIMS /* Compress adjacent delimiters */
               | WRDSF_PATHEXPAND     /* Expand pathnames */
               | WRDSF_SHOWERR);      /* Show errors */
if (rc == 0) {
    /* Success.  The resulting words are returned in the NULL-terminated
       array ws.ws_wordv.  Number of words is in ws.ws_wordc */
}
/* Reclaim the allocated memory */
wordsplit_free(&ws);

For a detailed discussion, please see the man page wordsplit(3) included in the package.

2 Description

The package is designed as a drop-in facility for use in larger programs. It consists of the following files:

wordsplit.h
Interface header.
wordsplit.c
Main source file.
wordsplit.3
Manual page.

For most uses, you will need only these three. The rest of files are for building the autotest-based testsuite:

wsp.c
Auxiliary test program.
wordsplit.at
The source for the testsuite.

3 Incorporating wordsplit into your project

The project is designed to be used as a git submodule. To incorporate it into your project, first select the location for the wordsplit directory within your project. Then add the submodule at this location. The rest is quite straightforward: you need to add wordsplit.c to your sources and add both wordsplit.c and wordsplit.h to the distributed files.

The following will describe each step in detail. For the rest of this discussion it is supposed that wordsplit is the name of the location selected for the submodule. It is also supposed that your project uses GNU autotools framework. If you are using plain makefiles, these instructions are easy to convert to such use as well.

To add the submodule do:

git submodule add git://git.gnu.org.ua/wordsplit.git wordsplit

There are two methods of including the sources to the project: direct incorporation and incorporation via VPATH.

3.1 Direct incorporation

Add the subdir-objects option to the invocation of AM_INIT_AUTOMAKE macro in your configure.ac:

AM_INIT_AUTOMAKE([subdir-objects])

In your Makefile.am, add both wordsplit/wordsplit.c and wordsplit/wordsplit.h to the sources and -Iwordsplit to the cpp flags. For example:

program_SOURCES = main.c \
                  wordsplit/wordsplit.c \
                  wordsplit/wordsplit.h
AM_CPPFLAGS = -I$(srcdir)/wordsplit

You can also put wordsplit.h in the noinst_HEADERS variable, if you like:

program_SOURCES = main.c \
                  wordsplit/wordsplit.c
noinst_HEADERS = wordsplit/wordsplit.h
AM_CPPFLAGS = -I$(srcdir)/wordsplit

If you are building an installable library and wish to export the wordsplit API, install wordsplit.h to $(pkgincludedir), e.g.

lib_LTLIBRARIES = libmy.la
libmy_la_SOURCES = main.c \
                   wordsplit/wordsplit.c
AM_CPPFLAGS = -I$(srcdir)/wordsplit
pkginclude_HEADERS = wordsplit/wordsplit.h

3.2 VPATH-based incorporation

Modify the VPATH variable in your Makefile.am:

VPATH += $(srcdir)/wordsplit

Notice the use of +=: it is necessary for the vpath builds to work.

Add wordsplit.c to the nodist_program_SOURCES variable:

nodist_program_SOURCES = wordsplit.c

The nodist_ prefix is necessary to prevent make from trying to distribute this file from the current directory (where it doesn't exist of course). During compilation it will be located using VPATH.

Finally, add both wordsplit/wordsplit.c and wordsplit/wordsplit.h to the EXTRA_DIST variable and modify AM_CPPFLAGS as shown in the previous section.

An example Makefile.am:

program_SOURCES = main.c
nodist_program_SOURCES = wordsplit.c
VPATH += $(srcdir)/wordsplit
EXTRA_DIST = wordsplit/wordsplit.c wordsplit/wordsplit.h
AM_CPPFLAGS = -I$(srcdir)/wordsplit

It is also possible to use LDADD as shown in the example below:

program_SOURCES = main.c
LDADD = wordsplit.o
VPATH += $(srcdir)/wordsplit
EXTRA_DIST = wordsplit/wordsplit.c wordsplit/wordsplit.h
AM_CPPFLAGS = -I$(srcdir)/wordsplit

4 The testsuite

The package contains two files for building the testsuite: wsp.c, which is used to build the auxiliary binary wsp, and wordsplit.at, which can be included to a GNU autotest-based testsuite source.

The discussion below is for those who wish to include wordsplit testsuite into their project. It assumes that the hosting project already has an autotest-based testsuite.

4.1 Additional files

To build the auxiliary tool wsp, you will need an additional file, wordsplit-version.h. Normally, it should contain only a definition of the macro or variable WORDSPLIT_VERSION. The following shell fragment can be used to create it:

version=$(cd wordsplit; git describe)
cat > wordsplit-version.h <<EOF
#define WORDSPLIT_VERSION "$version"
EOF

This file should be listed in the EXTRA_DIST variable to make sure it is distributed with the tarball.

4.2 testsuite.at

Include the file wordsplit.at to your testsuite.at:

m4_include(wordsplit.at)

4.3 Makefile.am

In the Makefile.am responsible for creating the testsuite, make sure that the path to the wordsplit module is passed to the autotest invocation, so that the above m4_include statement will work. The usual make goal to build the testsuite looks as follows:

$(TESTSUITE): package.m4 $(TESTSUITE_AT)
      $(AM_V_GEN)$(AUTOTEST) \
            -I $(srcdir)\
            -I $(top_srcdir)/wordsplit\
            testsuite.at -o $@.tmp
      $(AM_V_at)mv $@.tmp $@

Then, add the following fragment to build the auxiliary files:

# ###########################
# Wordsplit testsuite
# ###########################
EXTRA_DIST += wordsplit-version.h
$(srcdir)/wordsplit-version.h: $(top_srcdir)/configure.ac
      $(AM_V_GEN){\
        if test -e $(top_srcdir)/libmailutils/wordsplit/.git; then \
            wsversion=$$(cd $(top_srcdir)/libmailutils/wordsplit; git describe); \
        else \
            wsversion="unknown"; \
        fi;\
        echo "#define WORDSPLIT_VERSION \"$wsversion\"";\
        echo '#include <mailutils/wordsplit.h>'; } > \
       > $(srcdir)/wordsplit-version.h

noinst_PROGRAMS += wsp
wsp_SOURCES =
nodist_wsp_SOURCES = wsp.c
wsp.o: $(srcdir)/wordsplit-version.h
VPATH += $(top_srcdir)/libmailutils/wordsplit

5 History

First version of wordsplit appeared in March 2009 as a part of the Wydawca1 project. Its main usage was to assist in configuration file parsing. The parser subsystem proved to be quite useful and soon evolved into a separate project - Grecs2. Wordsplit had since been used (as a git submodule) in a number of other projects, such as GNU Dico3 and Direvent4, to name a few.

In 2010 the wordsplit sources were incorporated to the GNU Mailutils5 package, where they replaced the decommissioned argcv module. Mailutils has its own configuration package, therefore using Grecs was not expedient. The wordsplit sources had been exported from Grecs and incorporated into Mailutils. Since then Mailutils and Grecs versions or wordsplit were periodically synchronized.

Several other projects, such as GNU Rush6 and fileserv7, followed suit. It had therefore been decided that it was advisable to have wordsplit as a separate package which could be easily included in another project without incurring unnecessary overhead. This separate package was created on July 7, 2019.

By the end of July 2019, all mentioned packages had switched to using wordsplit as a submodule.

6 Bug reporting

Please send bug reports, questions, suggestions and criticism via email to Sergey Poznyakoff or use the project's bug tracker. When sending bug reports, please make sure to provide the following information:

  1. Wordsplit invocation flags.
  2. Input string.
  3. Produced output.
  4. Expected output.

7 Copying

Copyright (C) 2009-2020 Sergey Poznyakoff

Permission is granted to anyone to make or distribute verbatim copies of this document as received, in any medium, provided that the copyright notice and this permission notice are preserved, thus giving the recipient permission to redistribute in turn.

Permission is granted to distribute modified versions of this document, or of portions of it, under the above conditions, provided also that they carry prominent notices stating who last changed them.

Footnotes:

1

Wydawca - an automatic release submission daemon
Home: http://puszcza.gnu.org.ua/software/wydawca
Git: http://git.gnu.org.ua/cgit/wydawca.git

2

Grecs - a library for parsing structured configuration files
Home: https://puszcza.gnu.org.ua/projects/grecs
Git: http://git.gnu.org.ua/cgit/grecs.git

4

GNU Direvent - filesystem event watching daemon
Home: http://puszcza.gnu.org.ua/software/direvent
Git: http://git.gnu.org.ua/cgit/direvent.git

5

GNU Mailutils - a general-purpose mail package
Home: http://mailutils.org
Git: http://git.savannah.gnu.org/cgit/mailutils.git

6

GNU Rush - a restricted user shell for remote access
Home: http://puszcza.gnu.org.ua/software/rush
Git: http://git.gnu.org.ua/cgit/rush.git

7

fileserv - simple http server for serving static files
Home: https://puszcza.gnu.org.ua/projects/fileserv
Git: http://git.gnu.org.ua/cgit/fileserv.git

Author: Sergey Poznyakoff

Created: 2020-04-01 Wed 00:03

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