140 lines
3.9 KiB
C
140 lines
3.9 KiB
C
/* strings - print ASCII strings in a file Author: Peter S. Housel */
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/*
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This is a version of the BSD "strings" program for Minix. It is used
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to search a file for printable strings. To install,
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cc -o strings strings.c
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chmem =8000 strings
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Command: strings - search file for printable strings
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Syntax: strings [-] [-o] [-len] file ...
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Flags: - Search the entire file. If this option is not given, only
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the initialized data segment of files that appear to be
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"a.out" format is searched.
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-o Print the offset (in octal) with each string.
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-len Use "len" as the minimum string length. The default is 4.
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Examples: strings core
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strings -o a.out > str
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Strings searches the specified file(s) for printable ASCII strings (four
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or more printable characters followed by a newline or a null) and writes
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them to the standard output. This can be used to find out, for example, to
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find out what program a "core" file came from, what kinds of error messages
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are in an executable, or to see ASCII data hidden in a "binary" data file.
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P.S. The program doesn't use the "a.out.h" file posted last week by
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Dick van Veen, both because it was written before then, and because
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not everybody has a.out.h yet. Future revisions probably ought to, though.
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*/
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#include <ctype.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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/* Minix (8086 version) dependant definitions */
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#define SMALLMAGIC 0x04100301L /* small model a.out magic number */
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#define SEPARATEMAGIC 0x04200301L /* separate instruction/data a.out */
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#define HDR_MAGIC 0 /* 0'th long magic number */
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#define HDR_HSIZE 1 /* 1'st long size of header */
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#define HDR_TSIZE 2 /* 2'nd long size of text */
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#define HDR_DSIZE 3 /* 3'rd long size of init'ed data */
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#define HDR_BSIZE 4 /* 4'th long size of bss */
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#define HDR_TOTMEM 6 /* 6'th long total memory */
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#define HDR_LEN 8 /* total length of header */
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/* Miscellaneous definitions */
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#define STRLEN 4 /* default minimum string length */
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#define STRBUF 512 /* buffer length for strings */
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_PROTOTYPE(int main, (int argc, char **argv));
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_PROTOTYPE(void strings, (char *filename));
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_PROTOTYPE(void usage, (void));
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int strmin = STRLEN; /* minimum string length */
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int printoff = 0; /* print octal offset of each str */
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int objall = 0; /* search entire a.out file, not */
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/* Just initialized data segment */
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int main(argc, argv)
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int argc;
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char *argv[];
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{
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while ((++argv, --argc) && '-' == (*argv)[0]) {
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if (!strcmp(*argv, "-"))
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++objall;
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else if (!strcmp(*argv, "-o"))
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++printoff;
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else if (isdigit((*argv)[1]))
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strmin = atoi(&(*argv)[1]);
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else
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usage();
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}
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if (0 == argc) usage();
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while (argc--) strings(*argv++);
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return(0);
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}
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void strings(filename)
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char *filename;
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{
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char buf[STRBUF]; /* the strings buffer */
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char *bufptr; /* pointer into the strings buffer */
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FILE *input; /* input file */
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long header[HDR_LEN]; /* buffer for reading the header */
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long offset; /* file offset */
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long limit; /* limit, if doing data segment only */
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int c; /* input character */
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if (NULL == (input = fopen(filename, "r"))) {
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fprintf(stderr, "strings: ");
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perror(filename);
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exit(1);
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}
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if (HDR_LEN == fread(header, sizeof(long), (size_t)HDR_LEN, input)
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&& (SMALLMAGIC == header[HDR_MAGIC]
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||SEPARATEMAGIC == header[HDR_MAGIC]) && !objall) {
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offset = header[HDR_HSIZE] + header[HDR_TSIZE]; /* object file */
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limit = offset + header[HDR_DSIZE];
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} else {
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offset = 0L;
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limit = 0L;
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}
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fseek(input, offset, 0);
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bufptr = buf;
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while (!limit || offset < limit) {
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if (EOF == (c = getc(input))) break;
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if ((('\0' == c || '\n' == c) && bufptr - buf >= strmin)
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|| (bufptr - buf == STRBUF - 1)) {
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*bufptr = '\0';
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if (printoff) printf("%lo:", offset - (bufptr - buf));
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puts(buf);
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bufptr = buf;
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} else if ((' ' <= c && c < 0177) || '\t' == c)
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*bufptr++ = c;
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else
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bufptr = buf;
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++offset;
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}
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fclose(input);
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}
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void usage()
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{
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fprintf(stderr, "usage: strings [-] [-o] [-num] file ...\n");
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exit(1);
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}
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