exec | 易学教程

Using istringstream in C++

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问题 I have some code that utilizes fork, execlp, and wait to make two processes. The objective is to be able to repeatedly print a prompt and have the user enter a command with up to 4 arguments/options to the command. int main() { string command, argument; istringstream iss(argument); do { //prompt user for command to run cout << "Enter command: "; cin >> command >> argument; int pid, rs, status; //fork will make 2 processes pid = fork(); if(pid == -1) { perror("fork"); exit(EXIT_FAILURE); } if

Run bat file in Java and wait 2

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问题 This is a followup question to my other question : Run bat file in Java and wait The reason i am posting this as a separate question is that the one i already asked was answered correctly. From some research i did my problem is unique to my case so i decided to create a new question. Please go read that question before continuing with this one as they are closely related. Running the proposed code blocks the program at the waitFor invocation. After some research i found that the waitFor

Run bat file in Java and wait 2

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Head First C 第九章进程与系统调用出错处理

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Head First C 第九章进程与系统调用出错处理大多数的系统调用以相同的方式出错需求：想知道系统调用为什么会失败，因此所有的系统调用都遵循“失败黄金法则”。尽可能的收拾残局把errno变量设为错误码返回-1 errno 变量是定义在 errno.h 中的全局变量，和它定义在一起的还有很多标准错误码。 EPERM=1 不允许操作 ENOENT=2 没有该文件或目录 ESRCH=3 没有该进程使用strerror打印标准错误 #include <errno.h> #include <stdio.h> #include <string.h> #include <unistd.h> int main() { if (execl("ifconfig", "ifconfig", NULL) == -1) if (execlp("kryptonite", "kryptonite", NULL) == -1) { fprintf(stderr, "Can not run ipconfig:%s\n", strerror(errno)); return 1; } return 0; } 系统调用在出错时通常会返回-1，但不是绝对的系统调用在出错的同时，将errno变量设为错误码。来源： oschina 链接： https://my.oschina.net/u/2491285

如何用Python交互执行shell脚本

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Python可以很方便的使用os.system()指定命令，调用shell脚本当然可以啦。但是有些命令或脚本是需要交互式的，从标准输入中得到选择才能继续往下执行，例如ssh登陆某个机器，需要你输入用户名、密码，你还想要看看回显结果，这显然不是一步解决的，怎么办呢? pexpect就是为解决这个问题诞生的。快去看看吧，非常好用哦: http://www.oschina.net/p/pexpect 来源： oschina 链接： https://my.oschina.net/u/266979/blog/94183

What are shell form and exec form?

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问题 What are shell form and exec form of commands? I have gone through several documents to get a clear idea of shell form and exec form. But all looked confusing to me. Can anyone help to figure out what are the difference between these two form? PS : Although I came across these terms while I was going through the docker file instructions( ex: RUN, CMD, ENTRYPOINT ), I want to know the difference between them in general, not in docker context. 回答1: The docker shell syntax (which is just a

Why does closing file descriptors after fork affect the child process?

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问题 I want to run programs in linux by a button click an therefore I wrote a function execute : void execute(const char* program_call, const char* param ) { pid_t child = vfork(); if(child == 0) // child process { int child_pid = getpid(); char *args[2]; // arguments for exec args[0] = (char*)program_call; // first argument is program_call args[1] = (char*)param; // close all opened file descriptors: const char* prefix = "/proc/"; const char* suffix = "/fd/"; char child_proc_dir[16]; sprintf

Why does closing file descriptors after fork affect the child process?

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PHP Exec: Without Waiting, Without Discarding the Output, Without nohup

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问题 I need to run a command in PHP like this: exec('dosomething > saveit.txt'); Except I don't want PHP to wait for it to be complete. I also don't want to throw away the output, and I don't want to use nohup because I'm using that for something else in the same directory. I also tried pclose(popen('dosomething > saveit.txt','r')); and that didn't work, it still waited. 回答1: Add an ampersand to the end of the command, so: exec('dosomething > saveit.txt &'); 回答2: in the documentation of exec()

mod_python equivalent to php exec() command

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问题 what is the mod_python equivalent to the php exec command? $cmd = '/var/www/scripts/test.py' + $parameter $return = exec($cmd) I've tried this but it doesn't return anything varReturn= subprocess.check_output(['/var/www/scripts/resolveID.py ', varParameters) 回答1: Capture the stdout and stderr of the subprocess: from subprocess import Popen, PIPE proc = Popen(['/var/www/scripts/resolveId.py', 'arg1', 'arg2'], stdout=PIPE, stderr=PIPE) stdout, stderr = proc.communicate() 来源： https:/