stderr | 易学教程

send R diagnostic messages to stdout instead stderr

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问题 Looking for an options which let me to redirect R diagnostic messages (produces by message() ) to stdout , not stderr as it is by default. message manual states: The default handler sends the message to the stderr() connection. So the question is how can I change this default behavior? still leaving redirection of warning() and stop() intact. Already tried sink type='message' but it redirects all (messages, warnings, errors). If anyone is willing to test, this is sample script exec_test.R :

STDERR? What is it? What are its common uses?

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Curious about how the handle STDERR works? Lets keep it down to say Batch Files to keep it simple and focused? I know that many programming languages accept STDERR, so I don't know if maybe uses are different across the board or maybe there is a common function for all programming languages? If anyone can provide some examples on common usage that you have seen or an explanation of why someone may utilize it for ??? situation that would be awesome. Thanks in advance! Usually you would use stderr for error messages. If you run a program on the command line, you can capture its stdout and/or

How to capture the exit_code and stderr of the command that is run in C++?

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问题 I'm writing a c++ program that executes and outputs (in real-time) a shell script, makefile or just another program. However I would like to have my program return differently when there are errors or no error. #include "execxi.h" using namespace std; int execXI::run(string command) { FILE *in; char buff[512]; // is this the check for command execution exited with not 0? if(!(in = popen(command.c_str(), "r"))){ // I want to return the exit code and error message too if any return 1; } // this

Redirect perror output to fprintf(stderr, “ ”)

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问题 In case a system call function fails, we normally use perror to output the error message. I want to use fprintf to output the perror string. How can I do something like this: fprintf(stderr, perror output string here); 回答1: #include <errno.h> fprintf(stderr, "%s\n", strerror(errno)); Note: strerror doesn't apply \n to the end of the message 来源： https://stackoverflow.com/questions/5483120/redirect-perror-output-to-fprintfstderr

What is the point of System.err?

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问题 In UNIX, I'm supposed to write a Java file that will print "EXIT 1" to the standard error, and then exit with a status of 1. Here is my approach.. System.err.println("EXIT 1"); System.exit(1); Is this what I'm supposed to do? If so, how am I supposed to use it in the Unix shells? When I compile and run it in the bash, it just prints "EXIT 1" (so it does the same thing as System.out.println, why should I use "err"?). What is the "standard error" here? 回答1: Every running program has these three

解析nohup java -jar xxx &

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一直就知道 java -jar xx ctrl+c就退出了来自这个文 https://blog.csdn.net/wngpenghao/article/details/83022185 java -jar XXX.jar & 命令结尾没有 “&” ，则变成 “java -jar XXX.jar ” ，表示在当前ssh窗口，可按CTRL + C打断程序运行，或者直接关闭窗口，则程序直接退出命令结尾添加 “&” ，则变成 “java -jar XXX.jar &” ，表示在当窗口关闭时，程序才会中止运行。&代表让该命令在后台执行。 nohup java -jar XXX.jar > Log.log & 或者 nohup java -jar XXX.jar >> Log.log & 命令 "nohup java -jar XXX.jar &" 部分，表示不挂断运行命令,当账户退出或终端关闭时,程序仍然运行。注意，该作业的所有输出被重定向到nohup.out的文件中。命令 "nohup java -jar XXX.jar > Log.log &" 部分，表示不挂断运行命令,当账户退出或终端关闭时,程序仍然运行，并且该作业的所有输出被重定向到Log.log的文件中。“ > Log.log ” 该命令就是指定日志输出的文件。 ">>"表示将输出以追加的方式重定向到Log.log中。

How can I redirect R warning messages to STDOUT?

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I'm using a grid engine to run R scripts. The STDERR is taken seriously under this setup, so I would like to keep it clean and have only real/serious/fatal errors printed to STDERR. The problem is my R script generate various STDERR messages which are not really serious warnings... for example, scan seems to print to STDERR the number of items it read. Can I redirect (from within R) STDERR to STDOUT? Look at the help page for sink() : ‘sink’ diverts R output to a connection. If ‘file’ is a character string, a file connection with that name will be established for the duration of the diversion.

How can I catch a “failed to decode JSON” error message in Perl?

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So I am trying to load test a REST API which returns a JSON value. To do that I am creating multiple instances of the perl script. The Perl script basically calls that URL, and tries to decode_json . Obviously when substantial load is generated, it fails. Now the problem I face is- An error is displayed on command prompt but does not write that error message in a file. The error message is malformed JSON string, neither array, object, number, string or atom, at character offset 0 (before "Can't connect to 209...") at json_load_test.pl line 39. In all the three attempts below line 39 refers to:

【原创】日志输出到串口设备导致的问题

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问题场景：测试人员报告，业务 modb 作为 RabbitMQ 的消费者，消费消息的速度非常慢，慢到大约每秒 2 条左右，从而导致 RabbitMQ 的队列中积压了 4000+ 条消息。排查过程：先通过 top 命令定位一下 [root@upucore_1 ~]# top -Hp 8177 top - 09:50:33 up 34 min, 8 users, load average: 4.76, 4.32, 3.65 Tasks: 2 total, 0 running, 2 sleeping, 0 stopped, 0 zombie Cpu0 : 11.8%us, 11.8%sy, 0.0%ni, 76.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 11.1%us, 11.1%sy, 0.0%ni, 77.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu2 : 5.9%us, 11.8%sy, 0.0%ni, 82.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 23.5%us, 29.4%sy, 0.0%ni, 47.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu4 : 5.6%us, 5.6%sy, 0.0%ni, 88

Test stdout and stderr redirection in bash script

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I would like to test in my bash script where stdout and stderr are directed, or more precisely, if they have been redirected. Have you an idea ? The $* bash variable don't give me this info. Mat You should be able to use the -t test switch to tell if the output streams are tty s or not: if [ -t 1 ] ; then echo stdout is a terminal else echo stdout is not a terminal fi Use -t 0 for stdin . Use -t 2 for stderr . Technically there is no way of telling whether stdin/stdout/stderr are "redirected" because you don't know what's invoking your script. If it's not being invoked from another shell,