+++ /dev/null
-/*
- * tail.c - copy the last part of a file
- *
- * Version: 2008-1.01
- * Build: c89 -o tail tail.c
- * Source: <http://pdcore.sourceforge.net/>
- * Spec: <http://www.opengroup.org/onlinepubs/9699919799/utilities/tail.html>
- *
- * This is free and unencumbered software released into the public domain,
- * provided "as is", without warranty of any kind, express or implied. See the
- * file UNLICENSE and the website <http://unlicense.org> for further details.
- */
-
-
-#define _POSIX_SOURCE
-
-#include <ctype.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <locale.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#define USAGE "usage: tail [-f] [-c number] [-n number] [file]\n"
-#define NOMALLOC "Unable to allocate memory for read buffer"
-#define NOFOLLOW "tail: Option [-f] ignored; can only follow regular files and FIFOs\n"
-#define BADBYTES "Option [-c] requires non-zero byte offset"
-#define BADLINES "Option [-n] requires integer line offset"
-#define CNMUTEXCL "Options [-c] and [-n] are mutually exclusive"
-#define FVANISH "Followed file has vanished"
-#define FSHRUNK "Followed file has shrunk"
-#define SYSERR 1
-#define APPERR 0
-
-static int isdecint(char *s);
-static void tailfile(int fd, char *fn);
-static void tailbyteoffset(int fd, char *fn, int isregfile, ssize_t len);
-static void taillineoffset(int fd, char *fn, int isregfile, ssize_t len);
-static void copytoeof(int fd, char *fn);
-static void fatal(int errtype, char *s);
-
-static unsigned char* buf;
-static ssize_t bufsize, offset;
-static int optf, optc, optn;
-
-
-int main(int argc, char **argv)
-{
- extern int opterr, optind;
- extern char *optarg;
- int c, fd;
- char *fn;
-
- setlocale(LC_ALL, "");
- opterr = 0;
-
- /*
- * try to get a buffer _twice_ the size mandated by the standard as in
- * later processing we may be paging through the file in _half_ buffer
- * increments; this way we guarentee POSIX buffer size conformance
- */
- bufsize = sysconf(_SC_LINE_MAX) * 20; /* POSIX says [{LINE_MAX)*10] */
- bufsize = bufsize < 4096 ? 4096 : bufsize;
-
- if ((buf = malloc(bufsize)) == NULL)
- fatal(APPERR, NOMALLOC);
-
- while ((c = getopt(argc, argv, "fc:n:")) != -1)
- switch (c)
- {
- case 'f': /* follow file */
- optf = 1;
- break;
-
- case 'c': /* offset in bytes */
- optc = 1;
- offset = 0;
- if (*optarg && isdecint(optarg))
- {
- offset = atol(optarg);
- offset = isdigit(*optarg) ? -offset : offset;
- }
-
- if (offset == 0)
- fatal(APPERR, BADBYTES);
- else
- break;
-
- case 'n': /* offset in lines */
- optn = 1;
- if (*optarg && isdecint(optarg))
- {
- offset = atol(optarg);
- offset = isdigit(*optarg) ? -offset : offset;
-
- /* the standard says [-n 0] is OK, but [-n +0] isn't &_& */
- if (offset != 0 || (offset == 0 && *optarg != '+'))
- break;
- }
- fatal(APPERR, BADLINES);
-
- default:
- fprintf(stderr, USAGE);
- exit(1);
- }
-
- if (! optc && ! optn) /* if none, set the default options */
- {
- optn = 1;
- offset = -10;
- }
-
- if (optc && optn)
- fatal(APPERR, CNMUTEXCL);
-
- if (optind >= argc)
- tailfile(STDIN_FILENO, "stdin");
- else
- {
- fn = argv[optind++];
-
- if (strcmp(fn, "-") == 0)
- tailfile(STDIN_FILENO, "stdin");
- else
- if ((fd = open(fn, O_RDONLY)) == -1)
- fatal(SYSERR, fn);
- else
- {
- tailfile(fd, fn);
- if (close(fd) == -1)
- fatal(SYSERR, fn);
- }
- }
-
- return(0);
-}
-
-
-int isdecint(char *s)
-{
- int badch = 0;
- char *c = s;
-
- if (! (isdigit(*c) || *c == '+' || *c == '-'))
- badch = 1;
- else
- for (c++; *c; c++)
- if (! isdigit(*c))
- badch = 1;
-
- return (! badch);
-}
-
-
-void tailfile(int fd, char *fn)
-{
- struct stat sbuf;
- int isregfile;
- ssize_t n, len;
-
- if (fstat(fd, &sbuf) == -1)
- fatal(SYSERR, fn);
-
- if (S_ISREG(sbuf.st_mode))
- {
- isregfile = 1;
- len = sbuf.st_size;
- }
- else
- isregfile = len = 0;
-
- if (offset != 0) /* [-n 0] is permitted; but no point processing that */
- {
- if (optc)
- tailbyteoffset(fd, fn, isregfile, len);
- else
- taillineoffset(fd, fn, isregfile, len);
- }
-
- if (optf)
- {
- if (fd == STDIN_FILENO) /* can't follow; warn then exit no error */
- {
- fprintf(stderr, NOFOLLOW);
- exit(0);
- }
-
- while(1) /* follow forever */
- {
- sleep(1);
-
- if (isregfile) /* if we can, be polite to the user */
- {
- if (stat(fn, &sbuf) == -1)
- fatal(APPERR, FVANISH);
- else if (sbuf.st_size < len)
- fatal(APPERR, FSHRUNK);
-
- len = sbuf.st_size;
- }
-
- while ((n = read(fd, buf, bufsize)) > 0)
- if (write(STDOUT_FILENO, buf, n) != n)
- fatal(SYSERR, "stdout");
-
- if (n < 0)
- fatal(SYSERR, fn);
- }
- }
-}
-
-
-void tailbyteoffset(int fd, char *fn, int isregfile, ssize_t len)
-{
- ssize_t n, halfbuf;
-
- if (isregfile) /* should be seekable, so we'll do so; it's fastest */
- {
- if (offset > 0)
- offset = (offset - 1) > len ? len : offset - 1;
- else
- offset = (len + offset) > 0 ? len + offset : 0;
-
- if (lseek(fd, (off_t)offset, SEEK_SET) == (off_t)-1)
- fatal(SYSERR, fn);
-
- copytoeof(fd, fn);
- }
-
- else /* possibly non-seekable */
- {
- if (offset > 0) /* forwards through file */
- {
- offset--;
-
- while(1)
- {
- if ((n = read(fd, buf, bufsize)) < 0)
- fatal(SYSERR, fn);
-
- if (n == 0)
- offset = 0;
-
- if (offset <= n)
- break;
- else
- offset -= n;
- }
-
- if (write(STDOUT_FILENO, buf + offset, n - offset) != n - offset)
- fatal(SYSERR, "stdout");
-
- copytoeof(fd, fn);
- }
-
- else /* backwards through file; remember that offset is negative */
- {
- halfbuf = bufsize / 2;
-
- if ((n = read(fd, buf, bufsize)) < 0)
- fatal(SYSERR, fn);
-
- if (n < bufsize) /* we've got the whole file */
- {
- offset = (n + offset) < 0 ? 0 : n + offset;
- len = n - offset;
- }
-
- else /* we haven't got the whole file */
- {
- while(1) /* page through the file, half a buffer at a time */
- {
- memcpy(buf, buf + halfbuf, halfbuf);
-
- if ((n = read(fd, buf + halfbuf, halfbuf)) < 0)
- fatal(SYSERR, fn);
- else if (n < halfbuf)
- break;
- }
-
- offset = (halfbuf + n + offset) < 0 ? 0 : halfbuf + n + offset;
- len = halfbuf + n - offset;
- }
-
- if (write(STDOUT_FILENO, buf + offset, len) != len)
- fatal(SYSERR, "stdout");
- }
- }
-}
-
-
-void taillineoffset(int fd, char *fn, int isregfile, ssize_t len)
-{
- ssize_t n, i, halfbuf;
-
- if (offset > 0) /* forwards through file */
- {
- offset--;
-
- while(1)
- {
- if ((n = read(fd, buf, bufsize)) < 0)
- fatal(SYSERR, fn);
-
- if (n == 0)
- {
- offset = 0;
- break;
- }
-
- for (i = 0; i < n && offset > 0; i++)
- if (buf[i] == '\n')
- offset--;
-
- if (offset == 0)
- {
- offset = i;
- break;
- }
- }
-
- if (write(STDOUT_FILENO, buf + offset, n - offset) != n - offset)
- fatal(SYSERR, "stdout");
-
- copytoeof(fd, fn);
- }
-
- else /* backwards through file; remember that offset is negative */
- {
- if (isregfile && len > 0) /* should be seekable, so we'll do so */
- {
- n = (len - bufsize) < 0 ? 0 : len - bufsize;
-
- if (lseek(fd, (off_t)n, SEEK_SET) == (off_t)-1)
- fatal(SYSERR, fn);
-
- if ((n = read(fd, buf, bufsize)) < 0)
- fatal(SYSERR, fn);
-
- if (buf[n-1] == '\n')
- offset--;
-
- for (i = n - 1; i >= 0 && offset < 0; i--)
- if (buf[i] == '\n')
- offset++;
-
- if (offset == 0)
- offset = i + 2;
- else
- offset = 0;
-
- len = n - offset;
-
- if (write(STDOUT_FILENO, buf + offset, len) != len)
- fatal(SYSERR, "stdout");
- }
-
- else
- {
- halfbuf = bufsize / 2;
-
- if ((n = read(fd, buf, bufsize)) < 0)
- fatal(SYSERR, fn);
-
- if (n < bufsize) /* we've got the whole file */
- {
- if (n == 0)
- offset = 0;
- else
- {
- if (buf[n-1] == '\n')
- offset--;
-
- for (i = n - 1; i >= 0 && offset < 0; i--)
- if (buf[i] == '\n')
- offset++;
-
- if (offset == 0)
- offset = i + 2;
- else
- offset = 0;
- }
-
- len = n - offset;
- }
-
- else /* we haven't got the whole file */
- {
- while(1) /* page through the file, half a buffer at a time */
- {
- memcpy(buf, buf + halfbuf, halfbuf);
-
- if ((n = read(fd, buf + halfbuf, halfbuf)) < 0)
- fatal(SYSERR, fn);
- else if (n < halfbuf)
- break;
- }
-
- if (buf[halfbuf+n-1] == '\n')
- offset--;
-
- for (i = halfbuf + n - 1; i >= 0 && offset < 0; i--)
- if (buf[i] == '\n')
- offset++;
-
- if (offset == 0)
- offset = i + 2;
- else
- offset = 0;
-
- len = halfbuf + n - offset;
- }
-
- if (write(STDOUT_FILENO, buf + offset, len) != len)
- fatal(SYSERR, "stdout");
- }
- }
-}
-
-
-void copytoeof(int fd, char *fn)
-{
- ssize_t n;
-
- while ((n = read(fd, buf, bufsize)) > 0)
- if (write(STDOUT_FILENO, buf, n) != n)
- fatal(SYSERR, "stdout");
-
- if (n < 0)
- fatal(SYSERR, fn);
-}
-
-
-void fatal(int errtype, char *s)
-{
- if (errtype == SYSERR)
- fprintf(stderr, "tail: %s: %s\n", s, strerror(errno));
- else
- fprintf(stderr, "tail: %s\n", s);
-
- exit(1);
-}
projects / pdutils / blobdiff