stderr

Given the following answer (first c++11 answer): How to execute a command and get output of command within C++ using POSIX? Here is the implementation for your convinience: #include <cstdio> #include <iostream> #include <memory> #include <stdexcept> #include <string> #include <array> std::string exec(const char* cmd) { std::array<char, 128> buffer; std::string result; std::shared_ptr<FILE> pipe(popen(cmd, "r"), pclose); if (!pipe) throw std::runtime_error("popen() failed!"); while (!feof(pipe.get())) { if (fgets(buffer.data(), 128, pipe.get()) != nullptr) result += buffer.data(); } return

三个默认的文件描述符 0 : stdin（标准输入） 1 : stdout（标准输出） 2 : stderr（标准错误输出） 系统中这3个文件描述符所对应的文件： 重定向顺序 示例脚本 echo "hello world" echo "xxx" sh test.sh hello world xxx sh test.sh >/tmp/out $ cat /tmp/out hello world xxx sh -x test.sh >/tmp/out 2>/tmp/err stdout和stderr分别被重定向到/tmp/out和/tmp/err。 $ cat /tmp/out hello world xxx $ cat /tmp/err + echo 'hello world' + echo xxx sh -x test.sh 2>&1 >/tmp/out stdout被重定向到/tmp/out，stderr被重定向到stdout。因为在执行2>&1的时候，stdout对应的文件为/dev/pts/2，所以stderr的输出仍为stdout，后面的stdout被重定向到/tmp/out。 $ sh -x test.sh 2>&1 >/tmp/out + echo 'hello world' + echo xxx $ cat /tmp/out hello world xxx 文件描述符

I'm having trouble piping the STDOUT & STDERR to a file when running a program as a systemd service. I've tried adding the following to the .service file: ExecStart=/apppath/appname > /filepath/filename 2>&1 But this doesn't work. The output is ending up in /var/log/messages and is viewable using journalctl but I'd like a separate file. I've also tried setting StdOutput=tty but can't find a way of redirecting this to a file. Any help would be appreciated. systemd.service(5) says: ExecStart= Commands with their arguments that are executed when this service is started. So, systemd runs your

I'm making a script that handles a predefined set of data, outputting to a file. I want to pop up a warning when one datum (which is always "Regular" in every set that I've had access to) is different stating that this value is unhandled (since I don't know how it affects the data). Should I output this warning to stderr or stdout? If I saved the output of this script (i.e. stdout only) so that I could process it later, would that warning interfere with how the output is parsed? Moreover, if output is piped to another process, the warning should show up on the terminal, so the user sees it

1. 对目录文件的操作包括创建、打开、定位和删除等内容， 其中 （1） 获取工作目录的函数有 getcwd 和 getwd 等。 （2） 设置工作目录的函数有 chdir 和 fchdir 等。 （3） 创建目录文件的函数有 mkdir 等。 （4） 删除目录文件的函数有 rmdir 等。 （5） 目录文件定位的函数有 seekdir 、 rewinddir 和 telldir 等。 2. 代码实例。 2.1 读取工作目录 ( 绝对路径 ) char *getcwd(char *buf, size_t size); char *getwd(char *pathname); /************ 实例 ***************/ #include <unistd.h> #include<stdio.h> int main() { char buf[255]; fprintf(stderr, “pwd = [%s]/n”, getcwd(buf, sizeof(buf)); chdir(“../”); fprintf(stderr, “pwd = [%s]/n”, getcwd(buf, sizeof(buf)); return 0; } 2.2 目录的创建与删除 int mkdir(const char *path, mode_t mode); int rmdir

To redirect (and append) stdout and stderr to a file, while also displaying it on the terminal, I do this: command 2>&1 | tee -a file.txt However, is there another way to do this such that I get an accurate value for the exit status? That is, if I test $? , I want to see the exit status of command , not the exit status of tee . I know that I can use ${PIPESTATUS[0]} here instead of $? , but I am looking for another solution that would not involve having to check PIPESTATUS . Perhaps you could put the exit value from PIPESTATUS into $? command 2>&1 | tee -a file.txt ; ( exit ${PIPESTATUS} )