/*
 * Copyright (c) 1988, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1988, 1993, 1994\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#if 0
#ifndef lint
static char sccsid[] = "@(#)env.c	8.3 (Berkeley) 4/2/94";
#endif /* not lint */
#endif

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/usr.bin/env/env.c,v 1.11 2002/09/04 23:28:59 dwmalone Exp $");

#include <sys/stat.h>
#include <sys/param.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

extern char	**environ;

/*
 * isspace() takes a parameter of 'int', but expect values in the range
 * of unsigned char.  Define a wrapper which takes a value of type 'char',
 * whether signed or unsigned, and ensure it ends up in the right range.
 */
#define	isalnumch(Anychar) isalnum((u_char)(Anychar))
#define	isalphach(Anychar) isalpha((u_char)(Anychar))
#define	isspacech(Anychar) isspace((u_char)(Anychar))

static int	 verbose;

static void	 expand_vars(char **thisarg_p, char **dest_p, const char
		    **src_p);
static int	 is_there(char *candidate);
static void	 search_paths(char *path, char **argv);
static void	 split_spaces(const char *str, int *origind, int *origc,
		    char ***origv);
static void	 usage(void);

int
main(int argc, char **argv)
{
	char **ep, *p, **parg, *altpath;
	char *cleanenv[1];
	int ch, want_clear;

	altpath = NULL;
	want_clear = 0;
	while ((ch = getopt(argc, argv, "-iP:S:v")) != -1)
		switch(ch) {
		case '-':
		case 'i':
			want_clear = 1;
			break;
		case 'P':
			altpath = strdup(optarg);
			break;
		case 'S':
			/*
			 * The -S option, for "split string on spaces, with
			 * support for some simple substitutions"...
			 */
			split_spaces(optarg, &optind, &argc, &argv);
			break;
		case 'v':
			verbose++;
			if (verbose > 1)
				fprintf(stderr, "#env verbosity now at %d\n",
				    verbose);
			break;
		case '?':
		default:
			usage();
		}
	if (want_clear) {
		environ = cleanenv;
		cleanenv[0] = NULL;
		if (verbose)
			fprintf(stderr, "#env clearing environ\n");
	}
	for (argv += optind; *argv && (p = strchr(*argv, '=')); ++argv) {
		if (verbose)
			fprintf(stderr, "#env setenv:\t%s\n", *argv);
		(void)setenv(*argv, ++p, 1);
	}
	if (*argv) {
		if (altpath)
			search_paths(altpath, argv);
		if (verbose) {
			fprintf(stderr, "#env executing:\t%s\n", *argv);
			for (parg = argv, argc = 0; *parg; parg++, argc++)
				fprintf(stderr, "#env    arg[%d]=\t'%s'\n",
				    argc, *parg);
			if (verbose > 1)
				sleep(1);
		}
		execvp(*argv, argv);
		err(errno == ENOENT ? 127 : 126, "%s", *argv);
	}
	for (ep = environ; *ep; ep++)
		(void)printf("%s\n", *ep);
	exit(0);
}

/*
 * Routine to determine if a given fully-qualified filename is executable.
 * This routine is copied almost verbatim from usr.bin/which/which.c.
 */
static int
is_there(char *candidate)
{
        struct stat fin;

        /* XXX work around access(2) false positives for superuser */
        if (access(candidate, X_OK) == 0 &&
            stat(candidate, &fin) == 0 &&
            S_ISREG(fin.st_mode) &&
            (getuid() != 0 ||
            (fin.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0)) {
                if (verbose > 1)
			fprintf(stderr, "#env   matched:\t'%s'\n", candidate);
                return (1);
        }
        return (0);
}

/**
 * Routine to search through an alternate path-list, looking for a given
 * filename to execute.  If the file is found, replace the original
 * unqualified name with a fully-qualified path.  This allows `env' to
 * execute programs from a specific strict list of possible paths, without
 * changing the value of PATH seen by the program which will be executed.
 * E.G.:
 *	#!/usr/bin/env -S-P/usr/local/bin:/usr/bin perl
 * will execute /usr/local/bin/perl or /usr/bin/perl (whichever is found
 * first), no matter what the current value of PATH is, and without
 * changing the value of PATH that the script will see when it runs.
 *
 * This is similar to the print_matches() routine in usr.bin/which/which.c.
 */
static void
search_paths(char *path, char **argv)
{
        char candidate[PATH_MAX];
        const char *d;
	char *filename, *fqname;

	/* If the file has a `/' in it, then no search is done */
	filename = *argv;
	if (strchr(filename, '/') != NULL)
		return;

	if (verbose > 1) {
		fprintf(stderr, "#env Searching:\t'%s'\n", path);
		fprintf(stderr, "#env  for file:\t'%s'\n", filename);
	}

	fqname = NULL;
        while ((d = strsep(&path, ":")) != NULL) {
                if (*d == '\0')
                        d = ".";
                if (snprintf(candidate, sizeof(candidate), "%s/%s", d,
                    filename) >= (int)sizeof(candidate))
                        continue;
                if (is_there(candidate)) {
                        fqname = candidate;
			break;
                }
        }

	if (fqname == NULL) {
		errno = ENOENT;
		err(127, "%s", filename);
	}
	*argv = strdup(candidate);
}

/**
 * Routine to split a string into multiple parameters, while recognizing a
 * few special characters.  It recognizes both single and double-quoted
 * strings.  This processing is designed entirely for the benefit of the
 * parsing of "#!"-lines (aka "shebang" lines == the first line of an
 * executable script).  Different operating systems parse that line in very
 * different ways, and this split-on-spaces processing is meant to provide
 * ways to specify arbitrary arguments on that line, no matter how the OS
 * parses it.
 *
 * Within a single-quoted string, the two characters "\'" are treated as
 * a literal "'" character to add to the string, and "\\" are treated as
 * a literal "\" character to add.  Other than that, all characters are
 * copied until the processing gets to a terminating "'".
 *
 * Within a double-quoted string, many more "\"-style escape sequences
 * are recognized, mostly copied from what is recognized in the `printf'
 * command.  Some OS's will not allow a literal blank character to be
 * included in the one argument that they recognize on a shebang-line,
 * so a few additional escape-sequences are defined to provide ways to
 * specify blanks.
 *
 * Within a double-quoted string "\_" is turned into a literal blank.
 * (Inside of a single-quoted string, the two characters are just copied)
 * Outside of a quoted string, "\_" is treated as both a blank, and the
 * end of the current argument.  So with a shelbang-line of:
 *		#!/usr/bin/env -SA=avalue\_perl
 * the -S value would be broken up into arguments "A=avalue" and "perl".
 */
static void
split_spaces(const char *str, int *origind, int *origc, char ***origv)
{
	const char *bq_src, *src;
	char *dest, **newargv, *newstr, **nextarg, **oldarg;
	int addcount, bq_destlen, copychar, found_sep, in_arg, in_dq, in_sq;

	/*
	 * Ignore leading space on the string, and then malloc enough room
	 * to build a copy of it.  The copy might end up shorter than the
	 * original, due to quoted strings and '\'-processing.
	 */
	while (isspacech(*str))
		str++;
	if (*str == '\0')
		return;
	newstr = malloc(strlen(str) + 1);

	/*
	 * Allocate plenty of space for the new array of arg-pointers,
	 * and start that array off with the first element of the old
	 * array.
	 */
	newargv = malloc((*origc + (strlen(str) / 2) + 2) * sizeof(char *));
	nextarg = newargv;
	*nextarg++ = **origv;

	/* Come up with the new args by splitting up the given string. */
	addcount = 0;
	bq_destlen = in_arg = in_dq = in_sq = 0;
	bq_src = NULL;
	for (src = str, dest = newstr; *src != '\0'; src++) {
		copychar = found_sep = 0;
		switch (*src) {
		case '"':
			if (in_sq)
				copychar = *src;
			else if (in_dq)
				in_dq = 0;
			else {
				in_dq = 1;
				bq_destlen = dest - *(nextarg - 1);
				bq_src = src;
			}
			break;
		case '$':
			if (in_sq)
				copychar = *src;
			else {
				expand_vars((nextarg - 1), &dest, &src);
			}
			break;
		case '\'':
			if (in_dq)
				copychar = *src;
			else if (in_sq)
				in_sq = 0;
			else {
				in_sq = 1;
				bq_destlen = dest - *(nextarg - 1);
				bq_src = src;
			}
			break;
		case '\\':
			if (in_sq) {
				/*
				 * Inside single-quoted strings, only the
				 * "\'" and "\\" are recognized as special
				 * strings.
				 */
				copychar = *(src + 1);
				if (copychar == '\'' || copychar == '\\')
					src++;
				else
					copychar = *src;
				break;
			}
			src++;
			switch (*src) {
			case '"':
			case '#':
			case '$':
			case '\'':
			case '\\':
				copychar = *src;
				break;
			case '_':
				/*
				 * Alternate way to get a blank, which allows
				 * that blank be used to separate arguments
				 * when it is not inside a quoted string.
				 */
				if (in_dq)
					copychar = ' ';
				else {
					found_sep = 1;
					src++;
				}
				break;
			case 'c':
				/*
				 * Ignore remaining characters in the -S string.
				 * This would not make sense if found in the
				 * middle of a quoted string.
				 */
				if (in_dq)
					errx(1, "Sequence '\\%c' is not allowed"
					    " in quoted strings", *src);
				goto str_done;
			case 'f':
				copychar = '\f';
				break;
			case 'n':
				copychar = '\n';
				break;
			case 'r':
				copychar = '\r';
				break;
			case 't':
				copychar = '\t';
				break;
			case 'v':
				copychar = '\v';
				break;
			default:
				if (isspacech(*src))
					copychar = *src;
				else
					errx(1, "Invalid sequence '\\%c' in -S",
					    *src);
			}
			break;
		default:
			if ((in_dq || in_sq) && in_arg)
				copychar = *src;
			else if (in_arg && isspacech(*src))
				found_sep = 1;
			else {
				/*
				 * If the first character of a new argument
				 * is `#', then ignore the remaining chars.
				 */
				if (!in_arg && *src == '#')
					goto str_done;
				copychar = *src;
			}
		}
		if (copychar) {
			if (!in_arg) {
				/* This is the first byte of a new argument */
				*nextarg++ = dest;
				addcount++;
				in_arg = 1;
			}
			*dest++ = (char)copychar;
		} else if (found_sep) {
			*dest++ = '\0';
			while (isspacech(*src))
				src++;
			--src;
			in_arg = 0;
		}
	}
str_done:
	*dest = '\0';
	*nextarg = NULL;
	if (in_dq || in_sq) {
		errx(1, "No terminating quote for string: %.*s%s",
		    bq_destlen, *(nextarg - 1), bq_src);
	}
	if (verbose > 1) {
		fprintf(stderr, "#env  split -S:\t'%s'\n", str);
		oldarg = newargv + 1;
		fprintf(stderr, "#env      into:\t'%s'\n", *oldarg);
		for (oldarg++; *oldarg; oldarg++)
			fprintf(stderr, "#env          &\t'%s'\n", *oldarg);
	}

	/* Copy the unprocessed arg-pointers from the original array */
	for (oldarg = *origv + *origind; *oldarg; oldarg++)
		*nextarg++ = *oldarg;
	*nextarg = NULL;

	/* Update optind/argc/argv in the calling routine */
	*origind = 1;
	*origc += addcount;
	*origv = newargv;
}

/**
 * Routine to split expand any environment variables referenced in the string
 * that -S is processing.  For now it only supports the form ${VARNAME}.  It
 * explicitly does not support $VARNAME, and obviously can not handle special
 * shell-variables such as $?, $*, $1, etc.  It is called with *src_p pointing
 * at the initial '$', and if successful it will update *src_p, *dest_p, and
 * possibly *thisarg_p in the calling routine.
 */
static void
expand_vars(char **thisarg_p, char **dest_p, const char **src_p)
{
	const char *vbegin, *vend, *vvalue;
	char *edest, *newstr, *vname;
	int bad_reference;
	size_t namelen, newlen;

	bad_reference = 1;
	vbegin = vend = (*src_p) + 1;
	if (*vbegin++ == '{')
		if (*vbegin == '_' || isalphach(*vbegin)) {
			vend = vbegin + 1;
			while (*vend == '_' || isalnumch(*vend))
				vend++;
			if (*vend == '}')
				bad_reference = 0;
		}
	if (bad_reference)
		errx(1, "Only ${VARNAME} expansion is supported, error at: %s",
		    *src_p);

	/*
	 * We now know we have a valid environment variable name, so update
	 * the caller's source-pointer to the last character in that reference,
	 * and then pick up the matching value.  If the variable is not found,
	 * or if it has a null value, then our work here is done.
	 */
	*src_p = vend;
	namelen = vend - vbegin + 1;
	vname = malloc(namelen);
	strlcpy(vname, vbegin, namelen);
	vvalue = getenv(vname);
	if (vvalue == NULL || *vvalue == '\0')
		return;

	/*
	 * There is some value to copy to the destination.  If the value is
	 * shorter than the ${VARNAME} reference that it replaces, then we
	 * can just copy the value to the existing destination.
	 */
	edest = *dest_p;
	if (strlen(vname) + 3 >= strlen(vvalue)) {
		while (*vvalue != '\0')
		    *edest++ = *vvalue++;
		*dest_p = edest;
		return;
	}

	/*
	 * The value is longer than the string it replaces, which means the
	 * present destination area is too small to hold it.  Create a new
	 * destination area, copy the present 'thisarg' value and the value
	 * of the referenced-variable to it, and then update the caller's
	 * 'thisarg' and 'dest' variables to match.
	 */
	*edest = '\0';			/* Provide terminator for 'thisarg' */
	newlen = strlen(*thisarg_p) + strlen(vvalue) + strlen(*src_p) + 1;
	newstr = malloc(newlen);
	strcpy(newstr, *thisarg_p);
	strcat(newstr, vvalue);
	*thisarg_p = newstr;
	*dest_p = strchr(newstr, '\0');
}

static void
usage(void)
{
	(void)fprintf(stderr,
	    "usage: env [-iv] [-P utilpath] [-S string] [name=value ...] [utility [argument ...]]\n");
	exit(1);
}