In the following program,
int main()
{
int fd;
char buf[8]={};
remove("file.txt");
fd = creat("file.txt",0666);
write(fd,"asdf",5);
perror("write");
lseek(fd,0,SEEK_SET);
perror("lseek");
read(fd,buf,5);
perror("read");
printf("%s\n",buf);
return 0;
}
My expected output is
write : Success
lseek : Success
Read : Success
asdf
But it shows
wriet : Success
lseek : Success
Read : Bad file descriptor
Can anybody tell me the reason? I can see that the string "asdf" if successfully written to file.txt
From the manpage:
The creat() function shall behave as if it is implemented as follows:
int creat(const char *path, mode_t mode) { return open(path, O_WRONLY|O_CREAT|O_TRUNC, mode); }
So, the file is opened in write-only mode and thus you cannot read.
If you need to read and write, use open(...) directly with O_RDWR instead of O_WRONLY.
0666 you specified just indicates the permissions in the file system the file gets created with.If you just want to do normal file I/O you could also use the high-level APIs such as fopen.
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