shell lab i/o

在Shell Lab中，实现了基本的shell功能和I/O重定向功能，但不支持管道功能。\[2\]eval()函数用于对外壳命令行进行求值，handler()函数用于处理SIGINT，SIGCHLD和SIGTSTP信号。\[2\]在实现I/O重定向时，可以使用exec命令来替代当前shell并重新启动一个shell，这样可以清除任何现有环境，但不会覆盖当前的shell环境。\[3\]
#### 引用[.reference_title]
- *1* [CSAPP：ShellLab实验](https://blog.csdn.net/qq_41140987/article/details/105330458)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
- *2* [ICS shell lab总结](https://blog.csdn.net/PKU_ZZY/article/details/53310876)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
- *3* [shell中的I/O redirect](https://blog.csdn.net/shuangchen/article/details/5855660)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
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