/* * cat_noblock.c - open a file and display its contents, but exit rather than * wait for input. */ #include /* for errno */ #include /* for open */ #include /* standard I/O */ #include /* for exit */ #include /* for read */ #define MAX_BYTES 1024 * 4 int main(int argc, char *argv[]) { int fd; /* The file descriptor for the file to read */ size_t bytes; /* The number of bytes read */ char buffer[MAX_BYTES]; /* The buffer for the bytes */ /* Usage */ if (argc != 2) { printf("Usage: %s \n", argv[0]); puts("Reads the content of a file, but doesn't wait for input"); exit(-1); } /* Open the file for reading in non blocking mode */ fd = open(argv[1], O_RDONLY | O_NONBLOCK); /* If open failed */ if (fd == -1) { if (errno = EAGAIN) puts("Open would block"); else puts("Open failed"); exit(-1); } /* Read the file and output its contents */ do { int i; /* Read characters from the file */ bytes = read(fd, buffer, MAX_BYTES); /* If there's an error, report it and die */ if (bytes == -1) { if (errno = EAGAIN) puts("Normally I'd block, but you told me not to"); else puts("Another read error"); exit(-1); } /* Print the characters */ if (bytes > 0) { for (i = 0; i < bytes; i++) putchar(buffer[i]); } /* While there are no errors and the file isn't over */ } while (bytes > 0); return 0; }