stderr | 易学教程

c popen won't catch stderr

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问题 I\'m trying to use popen() to catch the stderr of a call, but of course it doesn\'t seem to be doing that. Any ideas? My code looks more or less like this: popen(\"nedit\", \"r\"); But I\'m getting all this garbage about non-utf8 on my screen... 回答1: popen gives you a file handle on a process' stdout, not its stderr. Its first argument is interpreted as a shell command, so you can do redirections in it: FILE *p = popen("prog 2>&1", "r"); or, if you don't want the stdout at all, FILE *p =

redirect stdout/stderr to a string

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问题 there has been many previous questions about redirecting stdout/stderr to a file. is there a way to redirect stdout/stderr to a string? 回答1: Yes, you can redirect it to an std::stringstream : std::stringstream buffer; std::streambuf * old = std::cout.rdbuf(buffer.rdbuf()); std::cout << "Bla" << std::endl; std::string text = buffer.str(); // text will now contain "Bla\n" You can use a simple guard class to make sure the buffer is always reset: struct cout_redirect { cout_redirect( std:

网络编程(二)

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一.socket(套接字) 1.基于TCP协议的socket通信 sever端 1 import socket 2 sk = socket.socket() 3 sk.bind(('127.0.0.1',8898)) #把地址绑定到套接字 4 sk.listen() #监听链接 5 conn,addr = sk.accept() #接受客户端链接 6 ret = conn.recv(1024) #接收客户端信息 7 print(ret) #打印客户端信息 8 conn.send(b'hi') #向客户端发送信息 9 conn.close() #关闭客户端套接字 10 sk.close() #关闭服务器套接字(可选) client端 import socket sk = socket.socket() # 创建客户套接字 sk.connect(('127.0.0.1',8898)) # 尝试连接服务器 sk.send(b'hello!') ret = sk.recv(1024) # 对话(发送/接收) print(ret) sk.close() # 关闭客户套接字 2.标准通信循环 server端 import socket server = socket.socket() # 生成一个对象 server.bind(('127.0.0.1',8080)) # 绑定ip和port

Bash script - store stderr in a variable [duplicate]

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问题 This question already has answers here : How to store standard error in a variable (16 answers) Closed 3 years ago . I\'m writing a script to backup a database. I have the following line: mysqldump --user=$dbuser --password=$dbpswd \\ --host=$host $mysqldb | gzip > $filename I want to assign the stderr to a variable, so that it will send an email to myself letting me know what happened if something goes wrong. I\'ve found solutions to redirect stderr to stdout, but I can\'t do that as the

How to redirect both stdout and stderr to a file [duplicate]

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问题 This question already has an answer here: How to redirect and append both stdout and stderr to a file with Bash? 7 answers I am running a bash script that creates a log file for the execution of the command I use the following Command1 >> log_file Command2 >> log_file This only sends the standard output and not the standard error which appears on the terminal. Can I log both the stderr and stdout logged to a file? 回答1: If you want to log to the same file: command1 >> log_file 2>&1 If you want

网络编程解决黏包现象

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个人感悟：首先我觉的要想学好一门语言不论是是什么语言：java ， C ，python ，PHP，都要弄明白网络请求与响应，过程，osi模型等，我觉的这个最基础的，但是今天我需要解决的是网络交互时发生的"黏包"问题，行了不啰嗦了让我们进入正题吧。黏包现象让我们基于tcp先制作一个远程执行命令的程序（命令ls -l ; lllllll ; pwd）这块我们需要注意下 res=subprocess.Popen(cmd.decode('utf-8'), shell=True, stderr=subprocess.PIPE, stdout=subprocess.PIPE) 的结果的编码是以当前所在的系统为准的，如果是windows，那么res.stdout.read()读出的就是GBK编码的，在接收端需要用GBK解码且只能从管道里读一次结果同时执行多条命令之后，得到的结果很可能只有一部分，在执行其他命令的时候又接收到之前执行的另外一部分结果，这种显现就是黏包那么我们现在来实现个黏包现象吧看我是怎么解决的的基于tcp协议实现的黏包 tcp - server #_*_coding:utf-8_*_ from socket import * import subprocess ip_port=('127.0.0.1',8888) BUFSIZE=1024 tcp

How to print to stderr in Python?

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问题 There are several ways to write to stderr: # Note: this first one does not work in Python 3 print >> sys.stderr, \"spam\" sys.stderr.write(\"spam\\n\") os.write(2, b\"spam\\n\") from __future__ import print_function print(\"spam\", file=sys.stderr) That seems to contradict zen of Python #13 † , so what\'s the difference here and are there any advantages or disadvantages to one way or the other? Which way should be used? † There should be one — and preferably only one — obvious way to do it.

Temporarily Redirect stdout/stderr

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问题 Is it possible to temporarily redirect stdout/stderr in Python (i.e. for the duration of a method)? Edit: The problem with the current solutions (which I at first remembered but then forgot) is that they don\'t redirect ; rather, they just replace the streams in their entirety. Hence, if a method has a local copy of one the variable for any reason (e.g. because the stream was passed as a parameter to something), it won\'t work. Any solutions? 回答1: To solve the issue that some function might

How to store standard error in a variable

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问题 Let\'s say I have a script like the following: useless.sh echo \"This Is Error\" 1>&2 echo \"This Is Output\" And I have another shell script: alsoUseless.sh ./useless.sh | sed \'s/Output/Useless/\' I want to capture \"This Is Error\", or any other stderr from useless.sh, into a variable. Let\'s call it ERROR. Notice that I am using stdout for something. I want to continue using stdout, so redirecting stderr into stdout is not helpful, in this case. So, basically, I want to do ./useless.sh 2>