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study/linux-travel/MINIX-1.5/1.5/Source/commands/grep.c
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263
study/linux-travel/MINIX-1.5/1.5/Source/commands/grep.c
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/* grep - search a file for a pattern Author: Norbert Schlenker */
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/* Norbert Schlenker (nfs@princeton.edu) 1990-02-08
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* Released into the public domain.
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*
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* Grep searches files for lines containing a pattern, as specified by
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* a regular expression, and prints those lines. It is invoked by:
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* grep [flags] [pattern] [file ...]
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*
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* Flags:
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* -e pattern useful when pattern begins with '-'
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* -l prints just file names, no lines (quietly overrides -n)
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* -n printed lines are preceded by relative line numbers
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* -s prints errors only (quietly overrides -l and -n)
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* -v prints lines which don't contain the pattern
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*
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* Semantic note:
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* If both -l and -v are specified, grep prints the names of those
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* files which do not contain the pattern *anywhere*.
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*
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* Exit:
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* Grep sets an exit status which can be tested by the caller.
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* Note that these settings are not necessarily compatible with
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* any other version of grep, especially when -v is specified.
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* Possible status values are:
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* 0 if any matches are found
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* 1 if no matches are found
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* 2 if syntax errors are detected or any file cannot be opened
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*/
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/* External interfaces */
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#include <regexp.h> /* Thanks to Henry Spencer */
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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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extern int getopt(); /* Thanks to Henry Spencer */
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extern char *optarg;
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extern int optind;
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/* Internal constants */
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#define MATCH 0 /* exit code: some match somewhere */
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#define NO_MATCH 1 /* exit code: no match on any line */
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#define FAILURE 2 /* exit code: syntax error or bad file name */
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/* Macros */
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#define SET_FLAG(c) (flags[(c)-'a'] = 1)
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#define FLAG(c) (flags[(c)-'a'] != 0)
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/* Private storage */
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static char *program; /* program name */
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static char flags[26]; /* invocation flags */
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static regexp *expression; /* compiled search pattern */
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/* Internal interfaces */
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static int match();
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static char *get_line();
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static void error_exit();
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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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int opt; /* option letter from getopt() */
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char *pattern; /* search pattern */
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int exit_status = NO_MATCH; /* exit status for our caller */
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int file_status; /* status of search in one file */
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FILE *input; /* input file (if not stdin) */
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program = argv[0];
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memset(flags, 0, sizeof(flags));
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pattern = (char *) NULL;
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/* Process any command line flags. */
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while ((opt = getopt(argc, argv, "e:lnsv")) != EOF) {
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if (opt == '?')
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exit_status = FAILURE;
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else
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if (opt == 'e')
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pattern = optarg;
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else
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SET_FLAG(opt);
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}
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/* Detect a few problems. */
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if ((exit_status == FAILURE) || (optind == argc && pattern == (char *) NULL))
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error_exit("Usage: %s [-lnsv] [-e] expression [file ...]\n");
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/* Ensure we have a usable pattern. */
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if (pattern == (char *) NULL)
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pattern = argv[optind++];
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if ((expression = regcomp(pattern)) == (regexp *) NULL)
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error_exit("%s: bad regular expression\n");
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/* Process the files appropriately. */
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if (optind == argc) { /* no file names - find pattern in stdin */
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exit_status = match(stdin, (char *) NULL, "<stdin>");
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}
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else
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if (optind + 1 == argc) { /* one file name - find pattern in it */
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if (strcmp(argv[optind], "-") == 0) {
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exit_status = match(stdin, (char *) NULL, "-");
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} else {
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if ((input = fopen(argv[optind], "r")) == (FILE *) NULL) {
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fprintf(stderr, "%s: couldn't open %s\n",
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program, argv[optind]);
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exit_status = FAILURE;
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}
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exit_status = match(input, (char *) NULL, argv[optind]);
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}
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}
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else
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while (optind < argc) { /* lots of file names - find pattern in all */
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if (strcmp(argv[optind], "-") == 0) {
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file_status = match(stdin, "-", "-");
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} else {
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if ((input = fopen(argv[optind], "r")) == (FILE *) NULL) {
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fprintf(stderr, "%s: couldn't open %s\n",
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program, argv[optind]);
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exit_status = FAILURE;
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} else {
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file_status = match(input, argv[optind], argv[optind]);
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fclose(input);
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}
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}
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if (exit_status != FAILURE)
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exit_status &= file_status;
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++optind;
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}
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exit(exit_status);
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}
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/* match - matches the lines of a file with the regular expression.
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* To improve performance when either -s or -l is specified, this
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* function handles those cases specially.
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*/
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static int match(input, label, filename)
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FILE *input;
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char *label;
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char *filename;
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{
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char *line; /* pointer to input line */
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long int lineno = 0; /* line number */
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int status = NO_MATCH; /* summary of what was found in this file */
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if (FLAG('s') || FLAG('l')) {
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while ((line = get_line(input)) != (char *) NULL)
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if (regexec(expression, line, 1)) {
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status = MATCH;
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break;
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}
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if (FLAG('l'))
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if ((!FLAG('v') && status == MATCH) ||
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( FLAG('v') && status == NO_MATCH))
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puts(filename);
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return status;
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}
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while ((line = get_line(input)) != (char *) NULL) {
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++lineno;
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if (regexec(expression, line, 1)) {
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status = MATCH;
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if (!FLAG('v')) {
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if (label != (char *) NULL)
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printf("%s:", label);
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if (FLAG('n'))
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printf("%ld:", lineno);
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puts(line);
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}
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} else {
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if (FLAG('v')) {
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if (label != (char *) NULL)
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printf("%s:", label);
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if (FLAG('n'))
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printf("%ld:", lineno);
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puts(line);
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}
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}
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}
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return status;
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}
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/* get_line - fetch a line from the input file
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* This function reads a line from the input file into a dynamically
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* allocated buffer. If the line is too long for the current buffer,
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* attempts will be made to increase its size to accomodate the line.
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* The trailing newline is stripped before returning to the caller.
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*/
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#define FIRST_BUFFER 256 /* first buffer size */
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static char *buf = (char *) NULL; /* input buffer */
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static size_t buf_size = 0; /* input buffer size */
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static char *get_line(input)
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FILE *input;
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{
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int n;
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register char *bp;
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register int c;
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char *new_buf;
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size_t new_size;
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if (buf_size == 0) {
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if ((buf = (char *) malloc(FIRST_BUFFER)) == (char *) NULL)
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error_exit("%s: not enough memory\n");
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buf_size = FIRST_BUFFER;
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}
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bp = buf;
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n = buf_size;
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while (1) {
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while (--n > 0 && (c = getc(input)) != EOF) {
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if (c == '\n') {
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*bp = '\0';
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return buf;
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}
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*bp++ = c;
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}
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if (c == EOF)
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return (ferror(input) || bp == buf) ? (char *) NULL : buf;
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new_size = buf_size << 1;
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if ((new_buf = (char *) realloc(buf, new_size)) == (char *) NULL) {
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fprintf(stderr, "%s: line too long - truncated\n", program);
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while ((c = getc(input)) != EOF && c != '\n') ;
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*bp = '\0';
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return buf;
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} else {
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bp = new_buf + (buf_size - 1);
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n = buf_size + 1;
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buf = new_buf;
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buf_size = new_size;
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}
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}
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}
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/* Regular expression code calls this routine to print errors. */
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void regerror(s)
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char *s;
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{
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fprintf(stderr, "regexp: %s\n", s);
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}
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/* Common exit point for outrageous errors. */
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static void error_exit(msg)
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char *msg;
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{
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fprintf(stderr, msg, program);
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exit(FAILURE);
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}
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