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#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <error.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int exiterr(const char *s)
{
perror(s);
exit(-1);
}
int main(int argc, char *argv[])
{
int i, n = 1;
int fd;
char *fn;
struct stat st;
if(argc == 4 && !strcmp("-n", argv[1])) {
n = atoi(argv[2]);
fn = argv[3];
} else if(argc != 2) {
fprintf(stderr, "usage: %s [-n <n>] <file> "
"-- call fadvise(DONTNEED) <n> times on file", argv[0]);
exit(1);
} else {
fn = argv[1];
}
fd = open(fn, O_RDONLY);
if(fd == -1)
exiterr("open");
if(fstat(fd, &st) == -1)
exiterr("fstat");
if(!S_ISREG(st.st_mode)) {
fprintf(stderr, "%s: S_ISREG: not a regular file", fn);
return EXIT_FAILURE;
}
if(st.st_size == 0) {
fprintf(stderr, "%s: file size is 0!\n", fn);
return EXIT_FAILURE;
}
for(i = 0; i < n; i++)
if(posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED) == -1)
exiterr("posix_fadvise");
return EXIT_SUCCESS;
}
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