Stderr

The standard error output stream (stderr) is typically used by a program to output error messages or diagnostics.

Stdout

The standard output stream (stdout) is the stream where a program writes its output data.



Use streams popen

Example

"You re probably still receiving emails because you re only redirecting stdout but not stderr;to redirect stderr to dev null use"

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Crontab email send

"Use to redirect stderr 2 to stdout 1 or fork the process and manually deal with all three streams;popen catches stdout not stderr"

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Prevent popen from showing a command's output

Fflush line much

Example

"With stdio 3 output streams that refer to terminal devices are line buffered like stdout while stderr is not buffered;the program above exits immediately after fprintf so stdout is fflush then"

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Buffering stdin & stdout

"I guess that is because stdout is buffered while stderr is not or not so much;so stderr get s fflush after the line agent no process killed is streamed while stdout is fflush after the script . somescript.sh exists"

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Order mismatch between stdout and stderr in bash

Better errors couple

Example

"Stderr is better than stdout for errors for a couple of reasons"

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Command line utility: how to make it right?

"If you use java.io.bufferedreader stdout stderr devices works better"

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How to use CLI application from node.js child process?

Output reader present

Example

"Finally simply having a reader present on the stdout is not going to be enough;you need to actively be reading from it and from stderr to prevent the process from hanging if it writes too much output"

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Running bash script from java

"Ffmpeg being built as a command line tool that can take it s input from stdin and output to stdout stderr it is more simple to use these capabilities than to try to have ffmpeg handle the http reading writing"

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Stream ffmpeg transcoding result to S3

Others

Example

This also allows you to redirect the stderr into the stdout which makes it easier to read

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How do I call this command via Java's Runtime.getRuntime().exec method?

So you need to redirect stderr of strace to stdout before piping to grep;this is because strace writes all its output to stderr not stdout

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Grep on strace only working with stderr to stdout

If you still want to expose stdout to see the start-up message for example use;you need to redirect stderr not stdout

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Redirecting python -m CGIHTTPserver 8080 to /dev/null

Standard error or stderr;of the two stdout is used more often both by internal commands like copy and by console utilities or external commands like find and others as well as by third-party console programs

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How do I make a Windows batch script completely silent?

To save subprocess s stdout and stderr is more complex because you should consume both streams concurrently to avoid a deadlock

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Displaying subprocess output to stdout and redirecting it

A better solution would be using this batch file the command for runs in a separate command process with cmd.exe c more precisely compspec c in background the command line dir outputs to handle stdout of started command process in bare format because of option b the file names with extension and with full path because of option s of all only non-hidden files because of option a-d-h attribute not directory and not hidden with file name index.js found in specified directory or any subdirectory because of option s;the error message output by dir to handle stderr on not finding anything matching these criteria is suppressed by redirecting to device nul

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Running multiple NodeJS projects at once with a batch file

See this running in an online interpreter at advice re best-practice usage prompts are conventionally written to stderr on unix so for prompting-related purposes retaining the original stdout isn t generally called for;prompting on stderr is what read -p does

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In Bash, how to print to stdout when it’s already redirected?

In other words instead of mis-using stderr like this - look into ways to gain more control over stdout

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Difference in Processing of System.err.print ans System.out.print

The fix is to redirect stderr or redirect both stdout and stderr background when processes are initially created they generally always have three initial file descriptors already opened for them 0 stdin standard input a read-only stream 1 stdout standard output a write-only stream 2 stderr standard error a write-only stream there is precisely zero difference between stdout and stderr other than convention and the file descriptor number

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">" not working to direct output of python command to file

That is any thread that writes anything to stdout followed by a n that line will be printed on the terminal intact not interleaved;in contrast stderr is not buffered - it s output immediately which means that two threads writing to stderr simulatanouesly will cause the output to be interleaved

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Android Native libs - how are writes to log serialized

Consequently anything printed to stderr appears immediately while anything printed to stdout will be held until the buffer fills up on linux normally 8kb;note that when ls detects that stdout is not a terminal it sets the -1 flag by default one filename per line

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The order of stdout and stderr in bash

Stdout is line-buffered by default so that is relatively safe;stderr is not

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Pipe many outputs to same file at the same time?

Like stdout stderr is usually directed to the output device of the standard console generally the screen;that means stderr is not redirected to stdout but they share a common file descriptor

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Why is STDERR redirected to STDOUT

In general you shouldn t be writing to stdout at all from your library - even in a console application that could corrupt the output that the application is producing;stderr is a little more forgivable but you still shouldn t really use that unless the application requests it

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Error handling strategies in a shared library - C

Most posix-centric tools prescribe a very careful specification for their stdout stream so the tool s output can be piped elsewhere;stderr is much less prescribed and used liberally for logging and errors

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Why does "java -version" print its output to error stream?

Always stdout makes it easier to pipe to less grep it etc;if you are showing the help text because there was a problem with parsing the command line arguments then you might use stderr

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'app --help' should go to stdout or stderr?

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