0：\u6807\u51c6\u8f93\u5165（\u952e\u76d8）<\/p>\n<\/li>\n
1：\u6807\u51c6\u8f93\u51fa（\u663e\u793a\u5668）<\/p>\n<\/li>\n
2：\u6807\u51c6\u9519\u8bef（\u663e\u793a\u5668）
\n\u5206\u914d\u89c4\u5219：\u7cfb\u7edf\u5206\u914d fd \u65f6，\u6c38\u8fdc\u627e\u5f53\u524d\u672a\u88ab\u4f7f\u7528\u7684\u6700\u5c0f\u4e0b\u6807\u3002\u6240\u4ee5\u6211\u4eec\u65b0\u6253\u5f00\u7684\u6587\u4ef6\u9ed8\u8ba4\u662f 3；\u5982\u679c\u5173\u6389 0，\u65b0\u6253\u5f00\u7684\u6587\u4ef6\u5c31\u4f1a\u53d8\u6210 0\u3002<\/p>\n<\/li>\n<\/ul>\n
\u4e09\u3001 \u91cd\u5b9a\u5411\u7684\u672c\u8d28<\/h3>\n
\u6211\u4eec\u5e73\u65f6\u7528\u7684 >, >> \u7b26\u53f7，\u672c\u8d28\u4e0a\u662f\u6539\u53d8\u4e86 fd \u7684\u6307\u5411\u3002
\n\u5982\u679c\u6807\u51c6\u8f93\u51fa（1\u53f7）\u539f\u672c\u6307\u5411\u663e\u793a\u5668，\u6211\u4eec\u901a\u8fc7\u4ee3\u7801\u8ba9 1 \u53f7\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u6587\u4ef6，\u90a3\u4e48 printf \u8f93\u51fa\u7684\u5185\u5bb9\u5c31\u4f1a\u8dd1\u5230\u6587\u4ef6\u91cc\u3002
\n\u5b9e\u73b0\u8fd9\u4e2a\u9b54\u6cd5\u7684\u6838\u5fc3\u7cfb\u7edf\u8c03\u7528\u662f dup2(oldfd, newfd)\u3002\u5b83\u4f1a\u5c06 oldfd \u590d\u5236\u7ed9 newfd，\u8ba9 newfd \u4e5f\u6307\u5411\u540c\u4e00\u4e2a\u6587\u4ef6\u3002<\/p>\n
\u56db\u3001 \u5b9e\u6218\u4ee3\u7801：\u4f53\u9a8c\u91cd\u5b9a\u5411<\/h3>\n
int fd = open("log.txt", O_CREAT | O_WRONLY | O_TRUNC, 0644);
\n\/\/ \u6b64\u65f6 fd \u662f 3，\u6307\u5411 log.txt
\n\/\/ \u8ba9 1 \u53f7（\u6807\u51c6\u8f93\u51fa）\u4e5f\u6307\u5411 log.txt
\ndup2(fd, 1);
\n\/\/ \u63a5\u4e0b\u6765 printf \u7684\u5185\u5bb9\u5168\u90fd\u4f1a\u5199\u5165 log.txt，\u4e0d\u518d\u663e\u793a\u5728\u5c4f\u5e55\u4e0a
\nprintf("\u8fd9\u53e5\u8bdd\u88ab\u91cd\u5b9a\u5411\u5230\u6587\u4ef6\u4e86！\\\\n");
\nclose(fd);<\/p>\n
\u603b\u7ed3<\/h3>\n
\u201c\u4e00\u5207\u7686\u6587\u4ef6\u201d\u662f Linux \u7684\u6838\u5fc3\u54f2\u5b66\u3002\u901a\u8fc7\u6587\u4ef6\u63cf\u8ff0\u7b26，Linux \u628a\u786c\u4ef6（\u952e\u76d8\u3001\u663e\u793a\u5668）\u548c\u78c1\u76d8\u6587\u4ef6\u7edf\u4e00\u6210\u4e86\u540c\u4e00\u5957\u64cd\u4f5c\u63a5\u53e3\u3002\u638c\u63e1 dup2，\u5c31\u80fd\u7406\u89e3\u5404\u79cd\u91cd\u5b9a\u5411\u548c\u7ba1\u9053\u5e95\u5c42\u7684\u8fd0\u4f5c\u673a\u5236\u3002<\/p>\n
\u81ea\u6211\u5b9e\u6218\u64cd\u4f5c<\/h3>\n
cd ~\/linux_study
\nmkdir io_test
\ncd io_test<\/p>\n
\u5b9e\u6218 1：\u4f53\u9a8c\u7cfb\u7edf\u8c03\u7528 I\/O<\/h5>\n
vim sysio.c<\/p>\n
(\u8f93\u5165\u4ee5\u4e0b\u4ee3\u7801)<\/p>\n
#include <stdio.h>
\n#include <sys\/types.h>
\n#include <sys\/stat.h>
\n#include <fcntl.h>
\n#include <unistd.h>
\n#include <string.h><\/p>\n
int main() {
\n \/\/ \u6253\u5f00\u6587\u4ef6，\u5982\u679c\u6ca1\u6709\u5219\u521b\u5efa，\u6743\u9650\u8bbe\u4e3a 0644
\n int fd = open("test.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
\n if (fd < 0) {
\n perror("open");
\n return 1;
\n }<\/p>\n
printf("\u6210\u529f\u6253\u5f00\u6587\u4ef6，\u5f97\u5230\u7684 fd \u662f: %d\\\\n", fd); \/\/ \u5927\u6982\u7387\u662f 3<\/p>\n
const char *msg = "Hello System IO!\\\\n";
\n \/\/ \u7528\u7cfb\u7edf\u8c03\u7528 write \u5199\u5165
\n write(fd, msg, strlen(msg));<\/p>\n
close(fd);
\n return 0;
\n}<\/p>\n
\u7f16\u8bd1\u8fd0\u884c：<\/p>\n
gcc sysio.c -o sysio
\n.\/sysio
\ncat test.txt<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/10\/20261024105713-6adc8f09071a6.png\")
<\/p>\n
👉 \u4f60\u4f1a\u53d1\u73b0 fd \u662f 3\u3002\u56e0\u4e3a 0\u30011\u30012 \u88ab\u7cfb\u7edf\u5360\u7528\u4e86\u3002<\/p>\n
\u5b9e\u6218 2：\u9a8c\u8bc1 fd \u7684\u5206\u914d\u89c4\u5219<\/h5>\n
vim fd_rule.c<\/p>\n
(\u8f93\u5165\u4ee5\u4e0b\u4ee3\u7801)<\/p>\n
#include <stdio.h>
\n#include <sys\/types.h>
\n#include <sys\/stat.h>
\n#include <fcntl.h>
\n#include <unistd.h><\/p>\n
int main() {
\n close(0); \/\/ \u5173\u6389\u6807\u51c6\u8f93\u5165！
\n int fd = open("test.txt", O_RDONLY);
\n printf("\u5173\u6389 0 \u53f7\u540e，\u65b0\u6253\u5f00\u7684 fd \u662f: %d\\\\n", fd); \/\/ \u4f60\u4f1a\u53d1\u73b0\u53d8\u6210\u4e86 0！
\n close(fd);
\n return 0;
\n}<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/10\/20261024105713-6adc8f091b47d.png\")
<\/p>\n
(\u73b0\u8c61：\u7cfb\u7edf\u6c38\u8fdc\u627e\u6700\u5c0f\u7684\u7a7a\u4f4d\u3002\u8fd9\u8bc1\u660e\u4e86 fd \u5c31\u662f\u6570\u7ec4\u4e0b\u6807\u3002)<\/p>\n
\u5b9e\u6218 3：\u7528 dup2 \u5b8c\u6210\u8f93\u51fa\u91cd\u5b9a\u5411<\/h5>\n
vim redir.c<\/p>\n
(\u8f93\u5165\u4ee5\u4e0b\u4ee3\u7801)<\/p>\n
#include <stdio.h>
\n#include <unistd.h>
\n#include <fcntl.h><\/p>\n
int main() {
\n \/\/ 1. \u6253\u5f00\u4e00\u4e2a\u6587\u4ef6（\u6b64\u65f6 fd \u662f 3）
\n int fd = open("log.txt", O_CREAT | O_WRONLY | O_TRUNC, 0644);<\/p>\n
\/\/ 2. \u5c06 fd（3）\u590d\u5236\u7ed9 1（\u6807\u51c6\u8f93\u51fa）
\n \/\/ \u539f\u672c 1 \u6307\u5411\u663e\u793a\u5668，\u73b0\u5728 1 \u548c 3 \u6307\u5411\u540c\u4e00\u4e2a\u6587\u4ef6！
\n dup2(fd, 1); <\/p>\n
\/\/ 3. \u6b64\u65f6\u7528 printf \u8f93\u51fa，\u539f\u672c\u8be5\u4e0a\u5c4f\u5e55\u7684\u5b57，\u5168\u8fdb log.txt \u4e86！
\n printf("\u8fd9\u53e5\u8bdd\u4f1a\u88ab\u5199\u8fdb\u6587\u4ef6\u91cc！\\\\n");
\n printf("\u6807\u51c6\u8f93\u51fa\u5df2\u7ecf\u88ab\u91cd\u5b9a\u5411\u5566！\\\\n");<\/p>\n
close(fd);
\n return 0;
\n}<\/p>\n
\u7f16\u8bd1\u8fd0\u884c：<\/p>\n
gcc redir.c -o redir
\n.\/redir
\n# \u5c4f\u5e55\u4e0a\u4ec0\u4e48\u90fd\u4e0d\u4f1a\u663e\u793a！
\ncat log.txt # \u6253\u5f00\u6587\u4ef6\u770b，\u5b57\u5168\u5728\u91cc\u9762\u3002<\/p>\n
![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/10\/20261024105713-6adc8f092b723.png\")
<\/p>\n
\u5b9e\u6218 4：\u8fdb\u9636\u2014\u2014\u7ed9\u4e4b\u524d\u5199\u7684\u5fae\u578b Shell \u52a0\u4e0a\u91cd\u5b9a\u5411（\u9009\u505a）<\/h5>\n
\u7b2c\u4e00\u6b65：\u521b\u5efa\u65b0\u7684 Shell \u6587\u4ef6
\n\u8fdb\u5165\u76ee\u5f55，\u65b0\u5efa\u4e00\u4e2a\u6587\u4ef6：<\/p>\n
cd ~\/linux_study\/io_test
\nvim myshell_redir.c<\/p>\n
\u7b2c\u4e8c\u6b65：\u590d\u5236\u5e76\u4fdd\u5b58\u4ee5\u4e0b\u4ee3\u7801<\/p>\n
#include <stdio.h>
\n#include <stdlib.h>
\n#include <string.h>
\n#include <unistd.h>
\n#include <sys\/wait.h>
\n#include <sys\/types.h>
\n#include <sys\/stat.h>
\n#include <fcntl.h><\/p>\n
#define MAX_ARGS 10<\/p>\n
\/\/ \u5b9a\u4e49\u91cd\u5b9a\u5411\u7c7b\u578b
\n#define NoneRedir 0
\n#define OutputRedir 1 \/\/ >
\n#define AppRedir 2 \/\/ >><\/p>\n
int main() {
\n char buf[1024];
\n char *argv[MAX_ARGS];
\n int redir = NoneRedir;
\n char *filename = NULL;<\/p>\n
while (1) {
\n \/\/ \u6bcf\u6b21\u5faa\u73af\u91cd\u7f6e\u72b6\u6001
\n memset(argv, 0, sizeof(argv));
\n redir = NoneRedir;
\n filename = NULL;<\/p>\n
printf("myshell> ");
\n fflush(stdout);<\/p>\n
\/\/ 1. \u83b7\u53d6\u7528\u6237\u8f93\u5165
\n if (fgets(buf, sizeof(buf), stdin) == NULL) continue;
\n buf[strcspn(buf, "\\\\n")] = 0; \/\/ \u53bb\u9664\u6362\u884c\u7b26<\/p>\n
if (strcmp(buf, "exit") == 0) break;
\n if (strlen(buf) == 0) continue;<\/p>\n
\/\/ 2. \u89e3\u6790\u91cd\u5b9a\u5411（\u975e\u5e38\u7b80\u5355\u7c97\u66b4\u7684\u89e3\u6790：\u627e > \u6216 >>）
\n char *ptr = strstr(buf, ">>");
\n if (ptr != NULL) {
\n redir = AppRedir;
\n *ptr = '\\\\0'; \/\/ \u628a >> \u53d8\u6210\u5b57\u7b26\u4e32\u7ed3\u675f\u7b26，\u5207\u65ad\u524d\u9762\u547d\u4ee4
\n filename = ptr + 2; \/\/ \u6587\u4ef6\u540d\u5728 >> \u7684\u540e\u9762
\n while (*filename == ' ') filename++; \/\/ \u8df3\u8fc7\u7a7a\u683c
\n } else {
\n ptr = strchr(buf, '>');
\n if (ptr != NULL) {
\n redir = OutputRedir;
\n *ptr = '\\\\0'; \/\/ \u628a > \u53d8\u6210\u5b57\u7b26\u4e32\u7ed3\u675f\u7b26
\n filename = ptr + 1; \/\/ \u6587\u4ef6\u540d\u5728 > \u7684\u540e\u9762
\n while (*filename == ' ') filename++; \/\/ \u8df3\u8fc7\u7a7a\u683c
\n }
\n }<\/p>\n
\/\/ 3. \u89e3\u6790\u547d\u4ee4\u884c（\u6309\u7a7a\u683c\u5207\u5206，\u6ce8\u610f：\u6b64\u65f6 buf \u91cc\u53ea\u5269\u4e0b\u547d\u4ee4\u90e8\u5206\u4e86）
\n int argc = 0;
\n argv[argc] = strtok(buf, " ");
\n while (argv[argc] != NULL) {
\n argc++;
\n argv[argc] = strtok(NULL, " ");
\n }
\n if (argc == 0) continue; \/\/ \u7528\u6237\u53ea\u6572\u4e86\u56de\u8f66\u6216\u91cd\u5b9a\u5411\u7b26\u53f7<\/p>\n
\/\/ 4. Fork \u521b\u5efa\u5b50\u8fdb\u7a0b\u6267\u884c
\n pid_t pid = fork();
\n if (pid == 0) {
\n \/\/ — \u5b50\u8fdb\u7a0b\u5185\u90e8 —<\/p>\n
\/\/ \u6838\u5fc3：\u5904\u7406\u91cd\u5b9a\u5411！
\n if (redir != NoneRedir && filename != NULL) {
\n int fd = -1;
\n if (redir == OutputRedir) {
\n \/\/ \u4ee5\u5199\u65b9\u5f0f\u6253\u5f00，\u4e0d\u5b58\u5728\u5219\u521b\u5efa，\u5b58\u5728\u5219\u6e05\u7a7a
\n fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0644);
\n } else if (redir == AppRedir) {
\n \/\/ \u4ee5\u8ffd\u52a0\u65b9\u5f0f\u6253\u5f00，\u4e0d\u5b58\u5728\u5219\u521b\u5efa
\n fd = open(filename, O_WRONLY | O_CREAT | O_APPEND, 0644);
\n }<\/p>\n
if (fd < 0) {
\n perror("open error");
\n exit(1);
\n }<\/p>\n
\/\/ \u5c06\u6807\u51c6\u8f93\u51fa（1）\u6307\u5411\u6211\u4eec\u6253\u5f00\u7684\u6587\u4ef6
\n dup2(fd, 1);
\n close(fd); \/\/ \u590d\u5236\u5b8c\u5c31\u53ef\u4ee5\u5173\u6389\u539f\u6765\u7684 fd \u4e86
\n }<\/p>\n
\/\/ \u6267\u884c\u547d\u4ee4
\n execvp(argv[0], argv);
\n perror("execvp error"); \/\/ \u8d70\u5230\u8fd9\u8bf4\u660e\u547d\u4ee4\u6ca1\u627e\u5230
\n exit(1);
\n } else if (pid > 0) {
\n \/\/ \u7236\u8fdb\u7a0b\u7b49\u5f85\u56de\u6536
\n wait(NULL);
\n }
\n }
\n return 0;
\n}<\/p>\n
\u7b2c\u4e09\u6b65：\u7f16\u8bd1\u5e76\u8fd0\u884c<\/p>\n
gcc myshell_redir.c -o myshell_redir
\n.\/myshell_redir<\/p>\n
\u7b2c\u56db\u6b65：\u89c1\u8bc1\u5947\u8ff9\u7684\u65f6\u523b
\n\u5728 myshell> \u63d0\u793a\u7b26\u4e0b，\u4f9d\u6b21\u8f93\u5165\u4ee5\u4e0b\u547d\u4ee4\u4f53\u9a8c：<\/p>\n
\u6d4b\u8bd5\u666e\u901a\u547d\u4ee4：<\/p>\n
myshell> ls -l<\/p>\n
(\u5e94\u8be5\u6b63\u5e38\u5728\u5c4f\u5e55\u4e0a\u6253\u5370\u51fa\u5f53\u524d\u76ee\u5f55\u7684\u6587\u4ef6\u5217\u8868)<\/p>\n<\/li>\n
\u6d4b\u8bd5\u8f93\u51fa\u91cd\u5b9a\u5411 >：<\/p>\n
myshell> ls -l > out.txt<\/p>\n
(\u5c4f\u5e55\u4e0a\u4ec0\u4e48\u90fd\u4e0d\u6253\u5370，\u9000\u56de\u5230 myshell> \u63d0\u793a\u7b26\u3002\u6b64\u65f6\u4f60\u8f93\u5165 cat out.txt \u6216\u9000\u51fa shell \u540e\u770b，\u5185\u5bb9\u5168\u5728\u91cc\u9762)<\/p>\n<\/li>\n
\u6d4b\u8bd5\u8ffd\u52a0\u91cd\u5b9a\u5411 >>：<\/p>\n
myshell> echo "hello" >> out.txt
\nmyshell> echo "world" >> out.txt<\/p>\n
(\u518d\u7528 cat out.txt \u67e5\u770b，\u4f60\u4f1a\u53d1\u73b0 hello \u548c world \u90fd\u8ffd\u52a0\u8fdb\u53bb\u4e86，\u6ca1\u6709\u88ab\u8986\u76d6)<\/p>\n<\/li>\n
\u6d4b\u8bd5\u9519\u8bef\u547d\u4ee4：<\/p>\n
myshell> abcdefg<\/p>\n
(\u4f1a\u63d0\u793a execvp error: No such file or directory，\u56e0\u4e3a\u7cfb\u7edf\u627e\u4e0d\u5230\u8fd9\u4e2a\u547d\u4ee4)<\/p>\n<\/li>\n","protected":false},"excerpt":{"rendered":"
\u4e00\u3001 \u7cfb\u7edf\u8c03\u7528 vs \u5e93\u51fd\u6570\u6211\u4eec\u5e38\u7528 C \u8bed\u8a00\u7684 fopen\u3001printf，\u8fd9\u5c5e\u4e8e C \u6807\u51c6\u5e93\u51fd\u6570（\u7528\u6237\u6001）\u3002\u800c Linux \u7cfb\u7edf\u5e95\u5c42\u771f\u6b63\u5e72\u6d3b\u7684\u662f \u7cfb\u7edf\u8c03\u7528\u63a5\u53e3：open\u3001read\u3001write\u3001close\u3002
\n\u5e93\u51fd\u6570\u672c\u8d28\u4e0a\u662f\u5bf9\u7cfb\u7edf\u8c03\u7528\u7684\u5c01\u88c5，\u5e95\u5c42\u8fd8\u662f\u901a\u8fc7\u6587\u4ef6\u63cf\u8ff0\u7b26（fd）\u6765\u64cd\u4f5c\u3002\u4e8c\u3001 \u6df1\u5165\u7406\u89e3\u6587\u4ef6\u63cf\u8ff0\u7b26（fd）\u4f7f\u7528 open \u6253\u5f00\u6587\u4ef6\u540e，\u8fd4<\/p>\n","protected":false},"author":2,"featured_media":117386,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[58,371,305],"topic":[],"class_list":["post-117389","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-linux","tag-371","tag-305"],"yoast_head":"\n