Initial Commit

FILE_IO/1.FILE_OPEN/open_example.c

+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int main(int argc, char **argv){
+	
+	int fd = 0;
+	if(argc != 3)
+	{
+		fprintf(stderr, "usage: %s <file name> <access mode\n>", argv[0]);
+		fprintf(stderr, "access mode is octet number, ex:0775\n");
+		return 1;
+	}
+	
+	mode_t mode = 0;
+	sscanf(argv[2], "0%o", &mode);
+	fd = open(argv[1], O_WRONLY|O_CREAT|O_EXCL, mode);
+	if(fd == -1)
+	{
+		perror("failed open");
+		return 1;
+	}
+	
+	printf("success open %s\n", argv[1]);
+	close(fd);
+	
+	return 0;
+}

FILE_IO/2.FILE_READ_WRITE/rw_example.c

+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+int main(int argc, char **argv){
+	
+	int fd;
+	int rd;
+	char buf[256];
+	if(argc != 3)
+	{
+		fprintf(stderr, "usage: %s <file name> <data to add>\n", argv[0]);
+	}
+	
+	fd = open(argv[1], O_WRONLY|O_CREAT|O_APPEND, 0777);
+	if(fd == -1)
+	{
+		perror("failed open for write");
+		return 1;
+	}
+	
+	write(fd, argv[2], strlen(argv[2]));
+	write(fd, "\n", -1);
+	
+	close(fd);
+	
+	fd = open(argv[1], O_RDONLY, 0777);
+	if(fd == -1)
+	{
+		perror("failed open for read");
+		return 1;
+	}
+	memset(buf, 0, sizeof(buf));
+	
+	while((rd = read(fd, buf, sizeof(buf)))>0)
+	{
+		printf("%s\n", buf);
+	}
+	
+	close(fd);
+	
+	return 0;
+}

FILE_IO/2.FILE_READ_WRITE/test.txt

+System Programming is fun
\ No newline at end of file

FILE_IO/3.FILE_LSEEK/lseek_example.c

+#include <stdio.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int i, buf;
+	fd = open("num.dat", O_RDWR|O_CREAT);
+	
+	if(fd < 0)
+	{
+		perror("error : ");
+		exit(0);
+	}
+	
+	for (i=1000; i< 1010; i++)
+	{
+		write(fd, (void*)&i, sizeof(i));
+	}
+	
+	lseek(fd, 0, SEEK_SET);
+	read(fd, (void*)&buf, sizeof(i));
+	printf("%d\n", buf);
+	
+	lseek(fd, 4*sizeof(i), SEEK_SET);
+	read(fd, (void*)&buf, sizeof(i));
+	printf("%d\n", buf);
+}

FILE_IO/4.FILE_DUP/dup2_example.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int main()
+{
+	int fd = open("./dup2_example_data", O_CREAT|O_WRONLY, 0755);
+	
+	if(dup2(fd, STDOUT_FILENO) == -1)
+	{
+		perror("failed dup2");
+		return 1;
+	}
+	
+	printf("Hello World\n");
+	close(fd);
+	return 0;
+}

FILE_IO/4.FILE_DUP/dup2_example_data

+Hello World

FILE_IO/4.FILE_DUP/dup_example.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int main()
+{
+	int fd1 = open("./dup_example_data", O_CREAT|O_WRONLY, 0755);
+	write(fd1, "Hello\n", strlen("Hello\n"));
+	int fd2 = dup(fd1);
+	write(fd2, "Hi\n", strlen("Hi\n"));
+	close(fd1);
+	write(fd2, "nihao\n", strlen("nihao\n"));
+	close(fd2);
+	return 0;
+}

FILE_IO/4.FILE_DUP/dup_example_data

+Hello
+Hi
+nihao

FILE_IO/5.FILE_FCNTL/fcntl_example.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+int main(){
+	
+	int fd1 = 0, fd2 = 0, fd3 = 0;
+	fd1 = open("./fcntl_example_data", O_WRONLY|O_CREAT|O_TRUNC);
+	
+	printf("fcntl(F_DUPFD) TEST\n");
+	fd2 = fcntl(fd1, F_DUPFD, 30);
+	printf("fd2: %d\n", fd2);
+	
+	fd3 = fcntl(fd1, F_DUPFD, 30);
+	printf("fd2: %d\n", fd3);
+	
+	close(fd2);
+	close(fd3);
+	printf("dup2() TEST\n");
+	fd2 = dup2(fd1, 30);
+	printf("fd2: %d\n", fd2);
+	
+	fd3 = dup2(fd1, 30);
+	printf("fd3: %d\n", fd3);
+	
+	close(fd2);
+	close(fd3);
+	
+	close(fd1);
+	return 0;
+}