cat.c

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/* cat - concatenates files             Author: Andy Tanenbaum */

/* 30 March 1990 - Slightly modified for efficiency by Norbert Schlenker. */
/* 23 March 2002 - Proper error messages by Kees J. Bot. */


#include <errno.h>
#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <minix/minlib.h>
#include <stdio.h>

#define CHUNK_SIZE      (2048 * sizeof(char *))

static int unbuffered;
static char ibuf[CHUNK_SIZE];
static char obuf[CHUNK_SIZE];
static char *op = obuf;

int main(int argc, char **argv);
static void copyout(char *file, int fd);
static void output(char *buf, size_t count);
static void report(char *label);
static void fatal(char *label);

static char STDIN[] = "standard input";
static char STDOUT[] = "standard output";

static int excode = 0;

int main(int argc, char *argv[])
{
  int i, fd;

  i = 1;
  while (i < argc && argv[i][0] == '-') {
        char *opt = argv[i] + 1;

        if (opt[0] == 0) break;                         /* - */
        i++;
        if (opt[0] == '-' && opt[1] == 0) break;        /* -- */

        while (*opt != 0) switch (*opt++) {
        case 'u':
                unbuffered = 1;
                break;
        default:
                std_err("Usage: cat [-u] [file ...]\n");
                exit(1);
        }
  }

  if (i >= argc) {
        copyout(STDIN, STDIN_FILENO);
  } else {
        while (i < argc) {
                char *file = argv[i++];

                if (file[0] == '-' && file[1] == 0) {
                        copyout(STDIN, STDIN_FILENO);
                } else {
                        fd = open(file, O_RDONLY);
                        if (fd < 0) {
                                report(file);
                        } else {
                                copyout(file, fd);
                                close(fd);
                        }
                }
        }
  }
  output(obuf, (op - obuf));
  return(excode);
}

static void copyout(char *file, int fd)
{
  int n;

  while (1) {
        n = read(fd, ibuf, CHUNK_SIZE);
        if (n < 0) fatal(file);
        if (n == 0) return;
        if (unbuffered || (op == obuf && n == CHUNK_SIZE)) {
                output(ibuf, n);
        } else {
                int bytes_left;

                bytes_left = &obuf[CHUNK_SIZE] - op;
                if (n <= bytes_left) {
                        memcpy(op, ibuf, (size_t)n);
                        op += n;
                } else {
                        memcpy(op, ibuf, (size_t)bytes_left);
                        output(obuf, CHUNK_SIZE);
                        n -= bytes_left;
                        memcpy(obuf, ibuf + bytes_left, (size_t)n);
                        op = obuf + n;
                }
        }
  }
}

static void output(char *buf, size_t count)
{
  ssize_t n;

  while (count > 0) {
        n = write(STDOUT_FILENO, buf, count);
        if (n <= 0) {
                if (n < 0) fatal(STDOUT);
                std_err("cat: standard output: EOF\n");
                exit(1);
        }
        buf += n;
        count -= n;
  }
}

static void report(char *label)
{
  int e = errno;
  std_err("cat: ");
  std_err(label);
  std_err(": ");
  std_err(strerror(e));
  std_err("\n");
  excode = 1;
}

static void fatal(char *label)
{
  report(label);
  exit(1);
}

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