GEMini Atari/GEMini_Atari_CD-ROM_Walnut_Creek_December_1993.iso/zip/gnu/mntlib16.lzh/MNTLIB16/SYSTEM.C

C/C++ Source or Header | 1993-07-29 | 4KB | 199 lines

/*
 * system(): execute a command, passed as a string
 *
 * Written by Eric R. Smith and placed in the public domain.
 *
 * Modified by Allan Pratt to call _unx2dos on redirect file names
 * and to call spawnvp() without calling fork() -- why bother?
 *
 */

#include <limits.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <process.h>
#include <errno.h>
#include <file.h>
#include <osbind.h>
#include <unistd.h>
#include "lib.h"

#define isquote(c) ((c) == '\"' || (c) == '\'' || (c) == '`')
#define ARG_ERR       ( (Argentry *) -1 )

/* struct. used to build a list of arguments for the command */

typedef struct argentry {
    struct argentry *next;
    char    string[1];
} Argentry;


/* allocate an Argentry that will hold the string "s" */

static Argentry *_argalloc(s)
    const char *s;
{
    Argentry *x;

    x = (Argentry *) malloc((size_t)(sizeof(Argentry) + strlen(s) + 1));
    if (!x)
        return ARG_ERR;
    x->next = (Argentry *) 0;
    strcpy(x->string, s);
    return x;
}

/* free a list of Argentries */

static void _argfree(p)
    Argentry *p;
{
    Argentry *oldp;

    while (p) {
        oldp = p;
        p = p->next;
        free(oldp);
    }
}

/* parse a string into a list of Argentries. Words are defined to be
 * (1) any sequence of non-blank characters
 * (2) any sequence of characters starting with a ', ", or ` and ending
 *     with the same character. These quotes are stripped off.
 * (3) any spaces after an unquoted > or < are skipped, so
 *     "ls > junk" is parsed as 'ls' '>junk'.
 */

static Argentry *_parseargs(s)
    const char *s;
{
    Argentry *cur, *res;
    char buf[PATH_MAX];
    char *t, quote;

    res = cur = _argalloc("");

    for(;;) {
        t = buf;
again:
        while (isspace(*s)) s++;
        if (!*s) break;
        if (isquote(*s)) {
            quote = *s++;
            while (*s && *s != quote)
                *t++ = *s++;
            if (*s) s++;    /* skip final quote */
        }
        else {
            while (*s && !isspace(*s))
                *t++ = *s++;
            if (*s && ( *(s-1) == '>' || *(s-1) == '<' ))
                goto again;
        }
        *t = 0;
        cur->next = _argalloc(buf);
        if (!(cur = cur->next))      /* couldn't alloc() */
            return ARG_ERR;
    }
    cur->next = (Argentry *) 0;
    cur = res; res = res->next; free(cur);
    return res;
}


/* Here is system() itself.
 * FIXME: we probably should do wildcard expansion.
 * also, should errno get set here??
 */

int system(s)
    const char *s;
{
    Argentry *al, *cur;
    char **argv, *p;
    int  argc, i;
    char *infile, *outfile;
    int  infd = 0, outfd = 1, append = 0;
    int oldin = 0, oldout = 1;    /* hold the Fdup'd in, out */
    char path[PATH_MAX];
    int retval;

    if (!s)        /* check for system() supported ?? */
        return 1;
    al = _parseargs(s);        /* get a list of args */
    if (al == ARG_ERR) {        /* not enough memory */
        return errno = ENOMEM;
        return -1;
    }

    infile = outfile = "";

/* convert the list returned by _parseargs to the normal char *argv[] */
    argc = i = 0;
    for (cur = al; cur; cur = cur->next)
        argc++;
    if (!(argv = (char **) malloc((size_t)(argc * sizeof(char *))))) {
        errno = ENOMEM; return -1;
    }
    for (cur = al; cur; cur = cur->next) {
        p = cur->string;
        if (*p == '>') {
            outfile = p+1;
            if (*outfile == '>') {
                outfile++;
                append = 1;
            }
            else
            append = 0;
        }
        else if (*p == '<') {
            infile = p+1;
        }
        else
            argv[i++] = p;
    }
     argv[i] = (char *)0;

/* now actually run the program */

    if (*infile) {
        (void)_unx2dos(infile,path);
        infd = Fopen(path, 0);
        if (infd < __SMALLEST_VALID_HANDLE) {
            perror(infile);
            _exit(2);
        }
        oldin = Fdup(0);
        (void)Fforce(0, infd);
    }
    if (*outfile) {
        (void)_unx2dos(outfile,path);
        if (append) {
            outfd = Fopen(path, 2);
            if (outfd < __SMALLEST_VALID_HANDLE)
                outfd = Fcreate(path, 0);
            else
                (void)Fseek(0L, outfd, 2);
        }
        else
            outfd = Fcreate(path, 0);
        if (outfd < __SMALLEST_VALID_HANDLE) {
            perror(outfile);
            _exit(2);
        }
        oldout = Fdup(1);
        (void)Fforce(1, outfd);
    }

    retval = spawnvp(P_WAIT, argv[0], argv);

    if (*infile) (void)(Fforce(0,oldin), Fclose(oldin), Fclose(infd));
    if (*outfile) (void)(Fforce(1,oldout), Fclose(oldout), Fclose(outfd));
    free(argv);
    _argfree(al);
    return retval;
}