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Questions tagged [stderr]

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

The standard error stream, stderr, is a stream typically used by a program to output error or diagnostic messages. It is one of the three standard streams used by a UNIX-like program, along with and .

Like , stderr is outputted to the text terminal unless redirected.

The file descriptor for standard output is 2 (two); the POSIX definition is STDERR_FILENO.

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How to redirect and append both standard output and standard error to a file with Bash

To redirect standard output to a truncated file in Bash, I know to use: cmd > file.txt To redirect standard output in Bash, appending to a file, I know to use: cmd >> file.txt To redirect both standard output and standard error to a truncated…
flybywire
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How do I print to stderr in Python?

There are several ways to write to stderr: print >> sys.stderr, "spam" # Python 2 only. sys.stderr.write("spam\n") os.write(2, b"spam\n") from __future__ import print_function print("spam", file=sys.stderr) What are the differences between…
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How can I pipe stderr, and not stdout?

I have a program that writes information to stdout and stderr, and I need to process the stderr with grep, leaving stdout aside. Using a temporary file, one could do it in two steps: command > /dev/null 2> temp.file grep 'something' temp.file But…
user80168
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Redirect stderr and stdout in Bash

I want to redirect both standard output and standard error of a process to a single file. How do I do that in Bash?
flybywire
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How to redirect both stdout and stderr to a file

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.
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Confused about stdin, stdout and stderr?

I am rather confused with the purpose of these three files. If my understanding is correct, stdin is the file in which a program writes into its requests to run a task in the process, stdout is the file into which the kernel writes its output and…
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How to store standard error in a variable

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…
psycotica0
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Piping both stdout and stderr in bash?

It seems that newer versions of bash have the &> operator, which (if I understand correctly), redirects both stdout and stderr to a file (&>> appends to the file instead, as Adrian clarified). What's the simplest way to achieve the same thing, but…
Andrew Ferrier
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How can I print to standard error in C with 'printf'?

In C, printing to standard output (stdout) is easy, with printf from stdio.h. However, how can I print to standard error (stderr)? We can use fprintf to achieve it apparently, but its syntax seems strange. Maybe we can use printf to print to…
wad
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With bash, how can I pipe standard error into another process?

It's well known how to pipe the standard ouput of a process into another processes standard input: proc1 | proc2 But what if I want to send the standard error of proc1 to proc2 and leave the standard output going to its current location? You would…
paxdiablo
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How to redirect stderr to null in cmd.exe

I have an application that logs a lot of noise to stderr and REALLY slows down the execution of the application. I would like to redirect that output to null. Is this possible with cmd.exe?
Ignacio Soler Garcia
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Redirect all output to file using Bash on Linux?

I am trying to redirect all output from a command line programme to a file. I am using Bash. Some of the output is directed to a the file, but some still appears in the terminal and is not stored to the file. Similar symptoms are described…
Stefan
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Python: How to get stdout after running os.system?

I want to get the stdout in a variable after running the os.system call. Lets take this line as an example: batcmd="dir" result = os.system(batcmd) result will contain the error code (stderr 0 under Windows or 1 under some linux for the above…
Eduard Florinescu
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When should I use perror("...") and fprintf(stderr, "...")?

Reading the man pages and some code did not really help me in understanding the difference between - or better, when I should use - perror("...") or fprintf(stderr, "...").
freeboy1015
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Difference between $stdout and STDOUT in Ruby

In Ruby, what is the difference between $stdout (preceded by a dollar sign) and STDOUT (in all caps)? When doing output redirection, which should be used and why? The same goes for $stderr and STDERR. Edit: Just found a related question.
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