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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 =
      "@(#)$Id: file.c,v 1.3.2.1 1996/12/14 10:10:44 joerg 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() */
#if (__COHERENT__ >= 0x420)
#include <sys/utime.h>
#else
#include <utime.h>
#endif
#include <unistd.h>     /* for read() */

#ifdef __ELF__
#include <elf.h>
#endif

#include "patchlevel.h"
#include "file.h"

#ifdef S_IFLNK
# define USAGE  "Usage: %s [-vczL] [-f namefile] [-m magicfiles] file...\n"
#else
# define USAGE  "Usage: %s [-vcz] [-f namefile] [-m magicfiles] 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;  /* 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, app = 0;

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

      if (!(magicfile = getenv("MAGIC")))
            magicfile = MAGIC;

      while ((c = getopt(argc, argv, "vcdf:Lm:z")) != EOF)
            switch (c) {
            case 'v':
                  (void) fprintf(stdout, "%s-%d.%d\n", progname,
                               FILE_VERSION_MAJOR, patchlevel);
                  return 1;
            case 'c':
                  ++check;
                  break;
            case 'd':
                  ++debug;
                  break;
            case 'f':
                  if (!app) {
                        ret = apprentice(magicfile, check);
                        if (check)
                              exit(ret);
                        app = 1;
                  }
                  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);
      }

      if (!app) {
            ret = apprentice(magicfile, check);
            if (check)
                  exit(ret);
            app = 1;
      }

      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 */
      char match = '\0';

      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,
                     (int) (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 */
            match = tryit(buf, nbytes, zflag);
      }
#ifdef __ELF__
      /*
       * ELF executables have multiple section headers in arbitrary
       * file locations and thus file(1) cannot determine it from easily.
       * Instead we traverse thru all section headers until a symbol table
       * one is found or else the binary is stripped.
       * XXX: This will not work for binaries of a different byteorder.
       *    Should come up with a better fix.
       */

      if (match == 's' && nbytes > sizeof (Elf32_Ehdr) &&
          buf[EI_MAG0] == ELFMAG0 &&
          buf[EI_MAG1] == ELFMAG1 &&
          buf[EI_MAG2] == ELFMAG2 &&
          buf[EI_MAG3] == ELFMAG3) {

            union {
                  long l;
                  char c[sizeof (long)];
            } u;
            Elf32_Ehdr elfhdr;
            int stripped = 1;

            u.l = 1;
            (void) memcpy(&elfhdr, buf, sizeof elfhdr);

            /*
             * If the system byteorder does not equal the object byteorder
             * then don't test.
             */
            if ((u.c[sizeof(long) - 1] + 1) == elfhdr.e_ident[5]) {
                if (lseek(fd, elfhdr.e_shoff, SEEK_SET)<0)
                  error("lseek failed (%s).\n", strerror(errno));

                for ( ; elfhdr.e_shnum ; elfhdr.e_shnum--) {
                  if (read(fd, buf, elfhdr.e_shentsize)<0)
                      error("read failed (%s).\n", strerror(errno));
                  if (((Elf32_Shdr *)&buf)->sh_type == SHT_SYMTAB) {
                      stripped = 0;
                      break;
                  }
                }
                if (stripped)
                  (void) printf (", stripped");
            }
      }
#endif

      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');
}


int
tryit(buf, nb, zflag)
unsigned char *buf;
int nb, zflag;
{
      /* try compression stuff */
      if (zflag && zmagic(buf, nb))
            return 'z';

      /* try tests in /etc/magic (or surrogate magic file) */
      if (softmagic(buf, nb))
            return 's';

      /* try known keywords, check whether it is ASCII */
      if (ascmagic(buf, nb))
            return 'a';

      /* see if it's international language text */
      if (internatmagic(buf, nb))
            return 'i';

      /* abandon hope, all ye who remain here */
      ckfputs("data", stdout);
            return '\0';
}

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