--- /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