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#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
int main() {
char readBuffer[256] = {0};
char writeBuffer[] = "writeme";
int fl = open("/folder", O_RDWR);
printf("read from folder: %d\n", read(fl, readBuffer, sizeof readBuffer));
printf("errno: %d\n", errno);
errno = 0;
printf("write to folder: %d\n", write(fl, writeBuffer, sizeof writeBuffer));
printf("errno: %d\n\n", errno);
errno = 0;
int bd = open("/broken-device", O_RDWR);
printf("read from broken device: %d\n", read(bd, readBuffer, sizeof readBuffer));
printf("errno: %d\n", errno);
errno = 0;
printf("write to broken device: %d\n", write(bd, writeBuffer, sizeof writeBuffer));
printf("errno: %d\n\n", errno);
errno = 0;
int d = open("/device", O_RDWR);
printf("read from device: %d\n", read(d, readBuffer, sizeof readBuffer));
printf("data: %s\n", readBuffer);
memset(readBuffer, 0, sizeof readBuffer);
printf("errno: %d\n", errno);
errno = 0;
printf("write to device: %d\n", write(d, writeBuffer, sizeof writeBuffer));
printf("errno: %d\n\n", errno);
errno = 0;
int f = open("/file", O_RDWR);
printf("read from file: %d\n", read(f, readBuffer, sizeof readBuffer));
printf("data: %s\n", readBuffer);
memset(readBuffer, 0, sizeof readBuffer);
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, 3, SEEK_SET));
printf("errno: %d\n\n", errno);
printf("partial read from file: %d\n", read(f, readBuffer, 3));
printf("data: %s\n", readBuffer);
memset(readBuffer, 0, sizeof readBuffer);
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, -2, SEEK_END));
printf("errno: %d\n", errno);
errno = 0;
printf("partial read from end of file: %d\n", read(f, readBuffer, 3));
printf("data: %s\n", readBuffer);
memset(readBuffer, 0, sizeof readBuffer);
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, -15, SEEK_CUR));
printf("errno: %d\n", errno);
errno = 0;
printf("partial read from before start of file: %d\n", read(f, readBuffer, 3));
printf("data: %s\n", readBuffer);
memset(readBuffer, 0, sizeof readBuffer);
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, 0, SEEK_SET));
printf("write to start of file: %d\n", write(f, writeBuffer, 3));
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, 0, SEEK_END));
printf("write to end of file: %d\n", write(f, writeBuffer, 3));
printf("errno: %d\n\n", errno);
errno = 0;
printf("seek: %d\n", lseek(f, 10, SEEK_END));
printf("write after end of file: %d\n", write(f, writeBuffer, sizeof writeBuffer));
printf("errno: %d\n\n", errno);
errno = 0;
int bytesRead;
printf("seek: %d\n", lseek(f, 0, SEEK_SET));
printf("read after write: %d\n", bytesRead = read(f, readBuffer, sizeof readBuffer));
printf("errno: %d\n", errno);
errno = 0;
printf("final: ");
for (int i = 0; i < bytesRead; i++) {
if (readBuffer[i] == 0) {
printf("\\0");
} else {
printf("%c", readBuffer[i]);
}
}
printf("\n");
return 0;
}
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