[英]Getting file size with lseek command in c
我被要求找到文件usjng lseek命令的大小(不使用stat),我寫了以下代碼
int main() { char buf[100], fn[10]; int fd, i; printf("Enter file name\\n"); scanf("%s", fn); fd = open(fn, O_RDONLY); int size = lseek(fd, 0, SEEK_END); printf("Size is %d", size); close(fd); }
但是我的文件大小為-1,我在哪里出錯
從lseek
文檔在線獲取 :
返回值
成功完成后,lseek()返回結果偏移量位置,從文件開頭開始以字節為單位。 發生錯誤時,將返回值(off_t)-1,並且將errno設置為指示錯誤。
因此,您必須檢查errno
(如果lseek
返回-1
, errno
打印出來):
來自同一鏈接的可能錯誤列表:
錯誤
EBADF fd is not an open file descriptor. EINVAL whence is not valid. Or: the resulting file offset would be negative, or beyond the end of a seekable device. ENXIO whence is SEEK_DATA or SEEK_HOLE, and the file offset is beyond the end of the file. EOVERFLOW The resulting file offset cannot be represented in an off_t. ESPIPE fd is associated with a pipe, socket, or FIFO.
在您的情況下,很可能是EBADF。
以下建議的代碼:
現在建議的代碼:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
int main( void )
{
char fn[10];
int fd;
printf("Enter file name\n");
if( scanf("%9s", fn) != 1 )
{
fprintf( stderr, "scanf for file name failed\n" );
exit( EXIT_FAILURE );
}
if( (fd = open(fn, O_RDONLY) ) < 0 )
{
perror( "open failed" );
exit( EXIT_FAILURE );
}
off_t size = lseek(fd, 0, SEEK_END);
printf("Size is %ld", size);
close(fd);
}
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