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使用Python调用系统命令

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os.system() 该函数返回命令执行结果的返回值，system()函数在执行过程中进行了以下三步操作： 1、fork一个子进程； 2、在子进程中调用exec函数去执行命令； 3、在父进程中调用wait（阻塞）去等待子进程结束。返回0表示命令执行成功，其他表示失败。注意：使用该函数经常会莫名其妙地出现错误，但是直接执行命令并没有问题，所以一般建议不要使用。用法：os.system("command") os.popen() 这种调用方式是通过管道的方式来实现，函数返回是 file read 的对象，对其进行读取read、readlines等操作可以看到执行的输出。注意：如果命令执行失败，就读取不到内容。用法：os.popen("command") subprocess.Popen() subprocess模块被推荐用来替换一些老的模块和函数，如：os.system、os.spawn*、os.popen*等 subprocess模块目的是fork一个新的进程并与之通信，最常用是定义类Popen，使用Popen可以创建进程，并与进程进行复杂的交互。其函数原型为： class subprocess.Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn

CMake not redirecting stderr with execute_process

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I'm trying to redirect stdout and stderr to the same file using CMake. I'm using the execute_process option in CMake with the ERROR_FILE and OUTPUT_FILE option specified. I'm successfully capturing the output, but the error is not there. What am I doing wrong? File CMakeLists.txt add_test(NAME test${ID} COMMAND ${CMAKE_COMMAND} -DEXE=../examples/test${exampleID} -DID=${ID} -DARGS=${args} -P ${CMAKE_CURRENT_SOURCE_DIR}/Tester.cmake ) File Tester.cmake separate_arguments( ARGS ) # Run the test execute_process( COMMAND "${EXE}" ${ARGS} ERROR_FILE test${ID}.out OUTPUT_FILE test${ID}.out )

Redirect batch stderr to file

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问题 I have a batch file that executes a java application. I'm trying to modify it so that whenever an exception occurs, it'll write the STDERR out to a file. It looks something like this: start java something.jar method %1 %2 2>> log.txt Is there a way I can write the arguments %1 and %2 to the log.txt file as well? I don't want to write it to the log file everytime this batch file gets called, only when an exception occurs. I tried searching for a way to redirect STDERR into a variable, but I

stderr redirection methods

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问题 I am running tcsh/csh shell on my machine. lately i have realized my stderr file redirection is not working. Please find the terminal logs as below: >echo b c >>& log >cat log b c >echo $a b c >>& log a: Undefined variable. >cat log b c I have never faced such issues, hence not sure how to debug or troubleshoot. Please advice! An alterate method of redirection is using tee. While I use >& or >>& , i am altogether blocking any output to be displayed on terminal. Is there a way I can do both,

When redirecting in bash to stdout or stderr, I actually get redirected to a file

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问题 I'm saving the output of one command executed on a remote via ssh, but I also execute some echos. In order to see the messages on the screen and not save them to the variable I want to redirect them. I have tried >&1 and >&2 but in each case a file is created with the name either "1" or "2" Is this an issue of expanding quotes or escaping characters? OUTPUT=$(sshpass -p password ssh user@ip 'echo "Message1" >&2 ; su -lc "./rootscript.sh" >&2; echo "$?" ') echo "su output is: $OUTPUT" Output:

How to detect error (as in “Directory not found”, “TNS listener lost contact”, etc) in JSch?

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问题 I need to get error message while firing any command using JSch. Currently I am using below code to get output of tail command, but if the file does not exist, I should get the error as output (which I am not getting). public String getOutput() { LOGGER.debug("[getOutput]"); StringBuffer output = new StringBuffer(); InputStream in = null; if (channel != null && channel.isConnected()) { try { in = channel.getInputStream(); byte[] tmp = new byte[1024]; while (true) { LOGGER.debug("[getOutput]

CMake not redirecting stderr with execute_process

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问题 I'm trying to redirect stdout and stderr to the same file using CMake. I'm using the execute_process option in CMake with the ERROR_FILE and OUTPUT_FILE option specified. I'm successfully capturing the output, but the error is not there. What am I doing wrong? File CMakeLists.txt add_test(NAME test${ID} COMMAND ${CMAKE_COMMAND} -DEXE=../examples/test${exampleID} -DID=${ID} -DARGS=${args} -P ${CMAKE_CURRENT_SOURCE_DIR}/Tester.cmake ) File Tester.cmake separate_arguments( ARGS ) # Run the test

Tracing stdout and stderr in Tcl

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问题 I'm not sure if this absurd. Isn't it possible to trace the read and write of stdout and stderr in Tcl? I have tried the below and found no clue. % proc tracer {varname args} { upvar #0 $varname var puts "$varname value : $var" } % trace add variable stdout read tracer % trace add variable stdout write tracer % puts stdout hai hai % puts hai hai % trace add variable stderr write tracer % trace add variable stderr read tracer % puts hai hai % puts stderr hai hai As per the man page of puts ,

How to detect error (as in “Directory not found”, “TNS listener lost contact”, etc) in JSch?

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I need to get error message while firing any command using JSch. Currently I am using below code to get output of tail command, but if the file does not exist, I should get the error as output (which I am not getting). public String getOutput() { LOGGER.debug("[getOutput]"); StringBuffer output = new StringBuffer(); InputStream in = null; if (channel != null && channel.isConnected()) { try { in = channel.getInputStream(); byte[] tmp = new byte[1024]; while (true) { LOGGER.debug("[getOutput] in while"); while (in.available() > 0) { LOGGER.debug(in.available()); int i = in.read(tmp, 0, 1024); if

init script '/dev/tty: No such device or address' error on redirect

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问题 I will include the entire script at the bottom for reference. This script gets called toward the end of the init scripts. If I run the script after logging in, it runs with no error. 30000 foot view, trying to execute a rsync command and capture any errors into a variable. I am using bash 3.5.6pl. Here is the line that is the culprit: LogMessage+=$(rsync -rpltDzv --delete --progress /mnt/WinPrimary /mnt/WinBackup 2>&1 >/dev/tty)$'\n' What is stored in the variable, which does get written to a