usr.bin/file/file.c

/*
 * file - find type of a file or files - main program.
 *
 * Copyright (c) Ian F. Darwin, 1987.
 * Written by Ian F. Darwin.
 *
 * This software is not subject to any license of the American Telephone
 * and Telegraph Company or of the Regents of the University of California.
 *
 * Permission is granted to anyone to use this software for any purpose on
 * any computer system, and to alter it and redistribute it freely, subject
 * to the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of this
 *    software, no matter how awful, even if they arise from flaws in it.
 *
 * 2. The origin of this software must not be misrepresented, either by
 *    explicit claim or by omission.  Since few users ever read sources,
 *    credits must appear in the documentation.
 *
 * 3. Altered versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.  Since few users
 *    ever read sources, credits must appear in the documentation.
 *
 * 4. This notice may not be removed or altered.
 */
#ifndef lint
static char *moduleid =
        "@(#)file.c,v 1.2 1993/06/10 00:38:08 jtc Exp";
#endif  /* lint */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/param.h>  /* for MAXPATHLEN */
#include <sys/stat.h>
#include <fcntl.h>      /* for open() */
#include <utime.h>
#include <unistd.h>     /* for read() */

#include "file.h"

#ifdef S_IFLNK
# define USAGE  "Usage: %s [-czL] [-f namefile] [-m magicfile] file...\n"
#else
# define USAGE  "Usage: %s [-cz] [-f namefile] [-m magicfile] file...\n"
#endif

#ifndef MAGIC
# define MAGIC "/etc/magic"
#endif

int                     /* Global command-line options          */
        debug = 0,      /* debugging                            */
        lflag = 0,      /* follow Symlinks (BSD only)           */
        zflag = 0;      /* follow (uncompress) compressed files */

int                     /* Misc globals                         */
        nmagic = 0;     /* number of valid magic[]s             */

struct  magic *magic;   /* array of magic entries               */

char *magicfile = MAGIC;/* where magic be found                 */

char *progname;         /* used throughout                      */
int lineno;             /* line number in the magic file        */


static void unwrap      __P((char *fn));

/*
 * main - parse arguments and handle options
 */
int
main(argc, argv)
int argc;
char *argv[];
{
        int c;
        int check = 0, didsomefiles = 0, errflg = 0, ret = 0;

        if ((progname = strrchr(argv[0], '/')) != NULL)
                progname++;
        else
                progname = argv[0];

        while ((c = getopt(argc, argv, "cdf:Lm:z")) != EOF)
                switch (c) {
                case 'c':
                        ++check;
                        break;
                case 'd':
                        ++debug;
                        break;
                case 'f':
                        unwrap(optarg);
                        ++didsomefiles;
                        break;
#ifdef S_IFLNK
                case 'L':
                        ++lflag;
                        break;
#endif
                case 'm':
                        magicfile = optarg;
                        break;
                case 'z':
                        zflag++;
                        break;
                case '?':
                default:
                        errflg++;
                        break;
                }
        if (errflg) {
                (void) fprintf(stderr, USAGE, progname);
                exit(2);
        }

        ret = apprentice(magicfile, check);
        if (check)
                exit(ret);

        if (optind == argc) {
                if (!didsomefiles) {
                        (void)fprintf(stderr, USAGE, progname);
                        exit(2);
                }
        }
        else {
                int i, wid, nw;
                for (wid = 0, i = optind; i < argc; i++) {
                        nw = strlen(argv[i]);
                        if (nw > wid)
                                wid = nw;
                }
                for (; optind < argc; optind++)
                        process(argv[optind], wid);
        }

        return 0;
}


/*
 * unwrap -- read a file of filenames, do each one.
 */
static void
unwrap(fn)
char *fn;
{
        char buf[MAXPATHLEN];
        FILE *f;
        int wid = 0, cwid;

        if ((f = fopen(fn, "r")) == NULL) {
                error("Cannot open `%s' (%s).\n", fn, strerror(errno));
                /*NOTREACHED*/
        }

        while (fgets(buf, MAXPATHLEN, f) != NULL) {
                cwid = strlen(buf) - 1;
                if (cwid > wid)
                        wid = cwid;
        }

        rewind(f);

        while (fgets(buf, MAXPATHLEN, f) != NULL) {
                buf[strlen(buf)-1] = '\0';
                process(buf, wid);
        }

        (void) fclose(f);
}


/*
 * process - process input file
 */
void
process(inname, wid)
const char      *inname;
int wid;
{
        int     fd = 0;
        static  const char stdname[] = "standard input";
        unsigned char   buf[HOWMANY+1]; /* one extra for terminating '\0' */
        struct utimbuf  utbuf;
        struct stat     sb;
        int nbytes = 0; /* number of bytes read from a datafile */

        if (strcmp("-", inname) == 0) {
                if (fstat(0, &sb)<0) {
                        error("cannot fstat `%s' (%s).\n", stdname,
                              strerror(errno));
                        /*NOTREACHED*/
                }
                inname = stdname;
        }

        if (wid > 0)
             (void) printf("%s:%*s ", inname, wid - strlen(inname), "");

        if (inname != stdname) {
            /*
             * first try judging the file based on its filesystem status
             */
            if (fsmagic(inname, &sb) != 0) {
                    putchar('\n');
                    return;
            }

            if ((fd = open(inname, O_RDONLY)) < 0) {
                    /* We can't open it, but we were able to stat it. */
                    if (sb.st_mode & 0002) ckfputs("writeable, ", stdout);
                    if (sb.st_mode & 0111) ckfputs("executable, ", stdout);
                    ckfprintf(stdout, "can't read `%s' (%s).\n",
                        inname, strerror(errno));
                    return;
            }
        }


        /*
         * try looking at the first HOWMANY bytes
         */
        if ((nbytes = read(fd, (char *)buf, HOWMANY)) == -1) {
                error("read failed (%s).\n", strerror(errno));
                /*NOTREACHED*/
        }

        if (nbytes == 0)
                ckfputs("empty", stdout);
        else {
                buf[nbytes] = '\0';     /* null-terminate it */
                tryit(buf, nbytes);
        }

        if (inname != stdname) {
                /*
                 * Try to restore access, modification times if read it.
                 */
                utbuf.actime = sb.st_atime;
                utbuf.modtime = sb.st_mtime;
                (void) utime(inname, &utbuf); /* don't care if loses */
                (void) close(fd);
        }
        (void) putchar('\n');
}


void
tryit(buf, nb)
unsigned char *buf;
int nb;
{
        /*
         * try tests in /etc/magic (or surrogate magic file)
         */
        if (softmagic(buf, nb) != 1)
            /*
             * try known keywords, check for ascii-ness too.
             */
            if (ascmagic(buf, nb) != 1)
                /*
                 * abandon hope, all ye who remain here
                 */
                ckfputs("data", stdout);
}