How to Fix: How to redirect standard out and standard error to a file, and standard error (only) to console at the same time
Redirect standard output and error to a file while displaying error on console.
📋 Table of Contents
The issue described is a common problem faced by users who want to redirect standard output and error streams to a file, while also displaying only the standard error stream in the console. This can be frustrating when trying to troubleshoot or monitor system activity.
This guide aims to provide a step-by-step solution to this issue, explaining the root causes of the problem and offering two primary fix methods.
⚠️ Common Causes
- The primary cause of this issue is the use of incorrect redirection operators in the command. The `2>&1` operator redirects standard error to the same file as standard output, which can lead to unwanted output being displayed in the console.
- Another possible cause is the use of outdated or unsupported operating systems or shells, which may not support certain redirection operators.
🔧 Proven Troubleshooting Steps
Using the `tee` Command with Redirectors
- Step 1: Open a terminal and navigate to the directory where you want to save the output file.
- Step 2: Use the `mycommand` command followed by the redirection operator `2>&1 | tee test.txt`. This will redirect standard output to the same file as standard error, which can lead to unwanted output being displayed in the console.
- Step 3: To fix this issue, replace the `2>&1` operator with `2>/dev/null & 1>test.txt`. The `/dev/null` device redirects standard error to /dev/null, effectively discarding it, while `1>test.txt` redirects standard output to the file.
Using Process Substitution
- Step 1: Use the `mycommand` command followed by the redirection operator `2>&1 | tee test.txt & mycommand2`. This will redirect standard output to the same file as standard error, while also running another command in the background.
- Step 2: To fix this issue, use process substitution to redirect standard output and error streams separately. For example, `mycommand 2>/dev/null & 1>test.txt` redirects standard output to the file, while `mycommand2` runs independently.
🎯 Final Words
By following these steps, you should be able to redirect standard output and error streams to a file, while also displaying only the standard error stream in the console. Remember to test your commands carefully to ensure that they produce the desired output.
❓ Frequently Asked Questions
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