新建文件tailf.c文件

文件内容如下：

/* tailf.c -- tail a log file and then follow it

* Created: Tue Jan 9 15:49:21 1996 by faith@acm.org

* Copyright 1996, 2003 Rickard E. Faith (faith@acm.org)

*

* Permission is hereby granted, free of charge, to any person obtaining a

* copy of this software and associated documentation files (the "Software"),

* to deal in the Software without restriction, including without limitation

* the rights to use, copy, modify, merge, publish, distribute, sublicense,

* and/or sell copies of the Software, and to permit persons to whom the

* Software is furnished to do so, subject to the following conditions:

*

* The above copyright notice and this permission notice shall be included

* in all copies or substantial portions of the Software.

*

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR

* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,

* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

* OTHER DEALINGS IN THE SOFTWARE.

*

* less -F and tail -f cause a disk access every five seconds. This

* program avoids this problem by waiting for the file size to change.

* Hence, the file is not accessed, and the access time does not need to be

* flushed back to disk. This is sort of a "stealth" tail.

*/

#include

#include

#include

#include

#include

//#include "nls.h"

#define _(s) s

static size_t filesize(const char *filename)

{

struct stat sb;

if (!stat(filename, &sb)) return sb.st_size;

return 0;

}

static void tailf(const char *filename, int lines)

{

char **buffer;

int head = 0;

int tail = 0;

FILE *str;

int i;

if (!(str = fopen(filename, "r"))) {

fprintf(stderr, _("Cannot open \"%s\" for read\n"), filename);

perror("");

exit(1);

}

buffer = malloc(lines * sizeof(*buffer));

for (i = 0; i < lines; i++) buffer[i] = malloc(BUFSIZ + 1);

while (fgets(buffer[tail], BUFSIZ, str)) {

if (++tail >= lines) {

tail = 0;

head = 1;

}

}

if (head) {

for (i = tail; i < lines; i++) fputs(buffer[i], stdout);

for (i = 0; i < tail; i++) fputs(buffer[i], stdout);

} else {

for (i = head; i < tail; i++) fputs(buffer[i], stdout);

}

fflush(stdout);

for (i = 0; i < lines; i++) free(buffer[i]);

free(buffer);

}

int main(int argc, char **argv)

{

char buffer[BUFSIZ];

size_t osize, nsize;

FILE *str;

const char *filename;

int count;

//setlocale(LC_ALL, "");

//bindtextdomain(PACKAGE, LOCALEDIR);

//textdomain(PACKAGE);

if (argc != 2) {

fprintf(stderr, _("Usage: tailf logfile\n"));

exit(1);

}

filename = argv[1];

tailf(filename, 10);

for (osize = filesize(filename);;) {

nsize = filesize(filename);

if (nsize != osize) {

if (!(str = fopen(filename, "r"))) {

fprintf(stderr, _("Cannot open \"%s\" for read\n"), filename);

perror(argv[0]);

exit(1);

}

if (!fseek(str, osize, SEEK_SET))

while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0)

fwrite(buffer, 1, count, stdout);

fflush(stdout);

fclose(str);

osize = nsize;

}

usleep(250000); /* 250mS */

}

return 0;

}