kdelibs/kdecore/util/kshell.h

/*
    This file is part of the KDE libraries

    Copyright (c) 2003,2007 Oswald Buddenhagen <ossi@kde.org>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
*/
#ifndef KSHELL_H
#define KSHELL_H

#include <kdecore_export.h>

class QStringList;
class QString;

/**
 * \namespace KShell
 * Emulates some basic system shell functionality.
 * @see KStringHandler
 */
namespace KShell {

    /**
     * Flags for splitArgs().
     */
    enum Option {
        NoOptions = 0,

        /**
         * Perform tilde expansion.
         * On Windows, this flag is ignored, as the Windows shell has no
         * equivalent functionality.
         */
        TildeExpand = 1,

        /**
         * Put the parser into full shell mode and bail out if a too complex
         * construct is encoutered.
         * A particular purpose of this flag is finding out whether the
         * command line being split would be executable directly (via
         * KProcess::setProgram()) or whether it needs to be run through
         * a real shell (via KProcess::setShellCommand()). Note, however,
         * that shell builtins are @em not recognized - you need to do that
         * yourself (compare with a list of known commands or verify that an
         * executable exists for the named command).
         *
         * Meta characters that cause a bail-out are the command separators
         * @c semicolon and @c ampersand, the redirection symbols @c less-than,
         * @c greater-than and the @c pipe @c symbol and the grouping symbols
         * opening and closing @c parentheses.
         *
         * Further meta characters on *NIX are the grouping symbols
         * opening and closing @c braces, the command substitution symbol
         * @c backquote, the generic substitution symbol @c dollar (if
         * not followed by an apostrophe), the wildcards @c asterisk,
         * @c question @c mark and opening and closing @c square @c brackets
         * and the comment symbol @c hash @c mark.
         * Additionally, a variable assignment in the first word is recognized.
         *
         * A further meta character on Windows is the environment variable
         * expansion symbol @c percent. Occurrences of @c \%PERCENT_SIGN% as
         * inserted by quoteArg() are converted back and cause no bail-out,
         * though.
         */
        AbortOnMeta = 2
    };
    Q_DECLARE_FLAGS(Options, Option)

    /**
     * Status codes from splitArgs()
     */
    enum Errors {
        /**
         * Success.
         */
        NoError = 0,

        /**
         * Indicates a parsing error, like an unterminated quoted string.
         */
        BadQuoting,

        /**
         * The AbortOnMeta flag was set and an unhandled shell meta character
         * was encoutered.
         */
        FoundMeta
    };

    /**
     * Splits @p cmd according to system shell word splitting and quoting rules.
     * Can optionally perform tilde expansion and/or abort if it finds shell
     * meta characters it cannot process.
     *
     * On *NIX the behavior is based on the POSIX shell and bash:
     * - Whitespace splits tokens
     * - The backslash quotes the following character
     * - A string enclosed in single quotes is not split. No shell meta
     *   characters are interpreted.
     * - A string enclosed in double quotes is not split. Within the string,
     *   the backslash quotes shell meta characters - if it is followed
     *   by a "meaningless" character, the backslash is output verbatim.
     * - A string enclosed in $'' is not split. Within the string, the
     *   backslash has a similar meaning to the one in C strings. Consult
     *   the bash manual for more information.
     *
     * On Windows, the behavior is defined by the Microsoft C runtime. Qt and
     * many other implementations comply with this standard, but many do not.
     * - Whitespace splits tokens
     * - A string enclosed in double quotes is not split
     *   - 2N double quotes within a quoted string yield N literal quotes.
     *     This is not documented on MSDN.
     * - Backslashes have special semantics iff they are followed by a double
     *   quote:
     *   - 2N backslashes + double quote => N backslashes and begin/end quoting
     *   - 2N+1 backslashes + double quote => N backslashes + literal quote
     *
     * If AbortOnMeta is used on Windows, this function applies cmd shell
     * semantics before proceeding with word splitting:
     * - Cmd ignores @em all special chars between double quotes.
     *   Note that the quotes are @em not removed at this stage - the
     *   tokenization rules described above still apply.
     * - The @c circumflex is the escape char for everything including
     *   itself.
     *
     * @param cmd the command to split
     * @param flags operation flags, see \ref Option
     * @param err if not NULL, a status code will be stored at the pointer
     *  target, see \ref Errors
     * @return a list of unquoted words or an empty list if an error occurred
     */
    KDECORE_EXPORT QStringList splitArgs( const QString &cmd, Options flags = NoOptions, Errors *err = 0 );

    /**
     * Quotes and joins @p args together according to system shell rules.
     *
     * If the output is fed back into splitArgs(), the AbortOnMeta flag
     * needs to be used on Windows. On *NIX, no such requirement exists.
     *
     * See quoteArg() for more info.
     *
     * @param args a list of strings to quote and join
     * @return a command suitable for shell execution
     */
    KDECORE_EXPORT QString joinArgs( const QStringList &args );

    /**
     * Quotes @p arg according to system shell rules.
     *
     * This function can be used to quote an argument string such that
     * the shell processes it properly. This is e.g. necessary for
     * user-provided file names which may contain spaces or quotes.
     * It also prevents expansion of wild cards and environment variables.
     *
     * On *NIX, the output is POSIX shell compliant.
     * On Windows, it is compliant with the argument splitting code of the
     * Microsoft C runtime and the cmd shell used together.
     * Occurrences of the @c percent @c sign are replaced with
     * @c \%PERCENT_SIGN% to prevent spurious variable expansion;
     * related KDE functions are prepared for this.
     *
     * @param arg the argument to quote
     * @return the quoted argument
     */
    KDECORE_EXPORT QString quoteArg( const QString &arg );

    /**
     * Performs tilde expansion on @p path. Interprets "~/path" and
     * "~user/path". If the path starts with an escaped tilde ("\~" on UNIX,
     * "^~" on Windows), the escape char is removed and the path is returned
     * as is.
     *
     * Note that if @p path starts with a tilde but cannot be properly expanded,
     * this function will return an empty string.
     *
     * @param path the path to tilde-expand
     * @return the expanded path
     */
    KDECORE_EXPORT QString tildeExpand( const QString &path );
}

Q_DECLARE_OPERATORS_FOR_FLAGS(KShell::Options)

#endif /* KSHELL_H */