【在Linux世界中追寻伟大的One Piece】IO基础

<code class="javascript">#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>#include <string.h>int main(){FILE* fp = fopen("myfile", "w");if (!fp) {printf("fopen error!\n");}const char* msg = "One Piece!\n";int count = 5;while (count--) {fwrite(msg, strlen(msg), 1, fp);}fclose(fp);return 0;}</code>

<code class="javascript">#include <stdio.h>#include <string>int main(){FILE* fp = fopen("myfile", "r");if (!fp) {printf("fopen error!\n");}char buf[1024];const char* msg = "One Piece!\n";while (1) {//注意返回值和参数，此处有坑，仔细查看man手册关于该函数的说明size_t s = fread(buf, 1, strlen(msg), fp);if (s > 0) {buf[s] = 0;printf("%s", buf);}if (feof(fp)) {break;}}fclose(fp);return 0;}</code>

<code class="javascript">#include <stdio.h>#include <string.h>int main(){const char* msg = "hello fwrite\n";fwrite(msg, strlen(msg), 1, stdout);printf("hello printf\n");fprintf(stdout, "hello fprintf\n");return 0;}</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>#include <string.h>int main(){umask(0);int fd = open("myfile", O_WRONLY | O_CREAT, 0644);if (fd < 0) {perror("open");return 1;}int count = 5;const char* msg = "One Piece!\n";int len = strlen(msg);while (count--) {write(fd, msg, len);//msg：缓冲区首地址， len: 本次读取，期望写入多少个字节的数据。 返回值：实际写了多少字节数据}close(fd);return 0;}</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>#include <string.h>int main(){int fd = open("myfile", O_RDONLY);if (fd < 0) {perror("open");return 1;}const char* msg = "hello bit!\n";char buf[1024];while (1) {ssize_t s = read(fd, buf, strlen(msg));//类比writeif (s > 0) {printf("%s", buf);}else {break;}}close(fd);return 0;}</code>

<code class="javascript">#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>int open(const char* pathname, int flags);int open(const char* pathname, int flags, mode_t mode);</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <string.h>int main(){char buf[1024];size_t s = read(0, buf, sizeof(buf));if (s > 0) {buf[s] = 0;write(1, buf, strlen(buf));write(2, buf, strlen(buf));}return 0;}</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>int main(){int fd = open("myfile", O_RDONLY);if (fd < 0) {perror("open");return 1;}printf("fd: %d\n", fd);close(fd);return 0;}</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>int main(){close(0);//close(2);int fd = open("myfile", O_RDONLY);if (fd < 0) {perror("open");return 1;}printf("fd: %d\n", fd);close(fd);return 0;}</code>

<code class="javascript">#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdlib.h>int main(){close(1);int fd = open("myfile", O_WRONLY | O_CREAT, 00644);if (fd < 0) {perror("open");return 1;}printf("fd: %d\n", fd);fflush(stdout);close(fd);exit(0);}</code>

<code class="javascript">#include <stdio.h>#include <unistd.h>#include <fcntl.h>int main() {int fd = open("./log", O_CREAT | O_RDWR);if (fd < 0) {perror("open");return 1;}close(1);dup2(fd, 1);for (;;) {char buf[1024] = { 0 };ssize_t read_size = read(0, buf, sizeof(buf) - 1);if (read_size < 0) {perror("read");break;}printf("%s", buf);fflush(stdout);}return 0;}</code>

<code class="javascript"># include <stdio.h># include <stdlib.h># include <unistd.h># include <string.h># include <fcntl.h>char command[MAX_CMD];int do_face(){memset(command, 0x00, MAX_CMD);printf("minishell$ ");fflush(stdout);if (scanf("%[^\n]%*c", command) == 0) {getchar();return -1;}return 0;}char** do_parse(char* buff){int argc = 0;static char* argv[32];char* ptr = buff;while (*ptr != '\0') {if (!isspace(*ptr)) {argv[argc++] = ptr;while ((!isspace(*ptr)) && (*ptr) != '\0') {ptr++;}}else {while (isspace(*ptr)) {*ptr = '\0';ptr++;}}}argv[argc] = NULL;return argv;}int do_redirect(char* buff){char* ptr = buff, * file = NULL;int type = 0, fd, redirect_type = -1;while (*ptr != '\0') {if (*ptr == '>') {*ptr++ = '\0';redirect_type++;if (*ptr == '>') {*ptr++ = '\0';redirect_type++;}while (isspace(*ptr)) {ptr++;}file = ptr;while ((!isspace(*ptr)) && *ptr != '\0') {ptr++;}*ptr = '\0';if (redirect_type == 0) {fd = open(file, O_CREAT | O_TRUNC | O_WRONLY, 0664);}else {fd = open(file, O_CREAT | O_APPEND | O_WRONLY, 0664);}dup2(fd, 1);}ptr++;}return 0;}int do_exec(char* buff){char** argv = { NULL };int pid = fork();if (pid == 0) {do_redirect(buff);argv = do_parse(buff);if (argv[0] == NULL) {exit(-1);}execvp(argv[0], argv);}else {waitpid(pid, NULL, 0);}return 0;}int main(int argc, char* argv[]){while (1) {if (do_face() < 0)continue;do_exec(command);}return 0;}</code>

<code class="javascript">#include <stdio.h>#include <string.h>int main(){const char* msg0 = "hello printf\n";const char* msg1 = "hello fwrite\n";const char* msg2 = "hello write\n";printf("%s", msg0);fwrite(msg1, strlen(msg0), 1, stdout);write(1, msg2, strlen(msg2));fork();return 0;}</code>