LSEEK
文章目录
LSEEKlseek函数
lseek函数
lseek函数，定位到打开文件的指定位置处
#include <sys/types.h>
#include <unistd.h>
off_t
lseek(int fd
, off_t offset
, int whence
);
fd文件描述符offset偏移量whence在何处偏移
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
int main(int argc
, char *argv
[])
{
off_t offset
;
int fd
;
ssize_t numWritten
;
fd
= open(argv
[1], O_RDWR
| O_CREAT
,
S_IRUSR
| S_IWUSR
| S_IRGRP
| S_IWGRP
|
S_IROTH
| S_IWOTH
);
if (fd
== -1)
perror("open");
offset
= 10000;
if (lseek(fd
, offset
, SEEK_SET) == -1)
perror("lseek");
printf("%s: seek succeeded\n", "10000");
numWritten
= write(fd
, "abc", strlen("abc"));
printf("write = %ld\n", (long int)numWritten
);
if (close(fd
) == -1)
perror("close");
exit(0);
}
test
$
touch tfile
$ ./seek_io tfile
10000: seek succeeded
write = 3
$
ls -l tfile
-rw-rw-r-- 1 andrew andrew 10003 5月 25 23:27 tfile
说明打开文件之后，从文件开始处偏移10000之后有写入3个字符，所以为10003
