Echoing to stderr in Bash
The default error message variable for built-in Bash scripts is called stderr. It is also called standard error and is the default output device for errors.
Sometimes we have to redirect the error to an output channel. The Linux environment identifies each file object and its description, called FD.
It is a positive integer value identifying an open file session. For stderr, the file descriptor has the value 2.
In this article, we will learn about stderr and its functions. Also, we will look at some examples that will make the topic easier to understand.
Echoing to stderr in Bash
The command stderr is mainly used to keep a recode of the errors during the execution of any command. The general syntax of the command is:
Your command here 2>error.log
In the example syntax shared above, you can find a symbol 2> and a file called error.log. Now 2> represents the value of FILE DESCRIPTOR, which represents the identity of stderr.
In our case, the value of FILE DESCRIPTOR is 2. Now the file name we provide is for the log file generated during the command execution.
You can also echo stderr messages using the following syntax format.
Your command here >&2 echo "error"
Let's look at an example to simplify the topic. Suppose we have created an error command and want to echo the error message to the output.
Our example code will now look like this:
echo $( 3 + 2 )) >&2 echo "error"
In the code shared above, we have made a mistake intentionally to understand how it works. We have removed one of the brackets here, so this might be a mistake.
After that, we use echo to display the error. Running the above code will display the output as shown below.
./example.sh: line 1: syntax error near unexpected token `)'
./example.sh: line 1: `echo $( 3 + 2 )) >&2 echo "error" '
Now we correct the code as follows and run the command again.
echo $(( 3 + 2 )) >&2 "No error has been found."
After running the code, you will get the output as shown below.
5 No error has been found.
All the codes used in this article are written in Bash. It will only work in Linux Shell environment.
For reprinting, please send an email to 1244347461@qq.com for approval. After obtaining the author's consent, kindly include the source as a link.
Related Articles
How to decompress x.tar.xz format files under Linux
Publish Date：2025/04/08 Views：186 Category：OPERATING SYSTEM
-
A lot of software found today is in the tar.xz format, which is a lossless data compression file format that uses the LZMA compression algorithm. Like gzip and bzip2, it supports multiple file compression, but the convention is not to compr
Summary of vim common commands
Publish Date：2025/04/08 Views：115 Category：OPERATING SYSTEM
-
In Linux, the best editor should be vim. However, the complex commands behind vim's powerful functions also make us daunted. Of course, these commands do not need to be memorized by rote. As long as you practice using vim more, you can reme
Detailed explanation of command return value $? in Linux
Publish Date：2025/04/08 Views：58 Category：OPERATING SYSTEM
-
? is a special variable. This variable represents the return value of the previous command. That is to say, when we run certain commands, these commands will return a code after running. Generally, if the command is successfully run, the re
Common judgment formulas for Linux script shell
Publish Date：2025/04/08 Views：159 Category：OPERATING SYSTEM
-
In shell script programming, predicates are often used. There are two ways to use predicates, one is to use test, and the other is to use []. Let's take a look at how to use these two methods through two simple examples. Example 1 # test –
Shell script programming practice - specify a directory to delete files
Publish Date：2025/04/08 Views：98 Category：OPERATING SYSTEM
-
Usually, in Linux system we need to frequently delete some temporary files or junk files. If we delete them one by one manually, it will be quite troublesome. I have also been learning shell script programming recently, so I tried to write
Use of Linux command at - set time to execute command only once
Publish Date：2025/04/08 Views：158 Category：OPERATING SYSTEM
-
This article mainly involves a knowledge point, which is the atd service. Similar to this service is the crond service. The functions of these two services can be similar to the two functional functions of javascript. Those who have learned
Use of Linux command crontab - loop execution of set commands
Publish Date：2025/04/08 Views：170 Category：OPERATING SYSTEM
-
Compared with at , which executes a command only once, crontab, which we are going to talk about in this article, executes the set commands in a loop. Similarly, the use of crontab requires the support of the crond service. The service is s
Linux practice - regularly delete files under the directory
Publish Date：2025/04/08 Views：198 Category：OPERATING SYSTEM
-
Since we want to delete the files under the directory regularly, we need to use the Linux crontab command. And the content format of each work routine is also introduced in the format of each crontab work. Similarly, we need to use shell sc
How to use the Linux file remote copy command scp
Publish Date：2025/04/08 Views：151 Category：OPERATING SYSTEM
-
Scp copies files between two hosts over the network, and the data is encrypted during transmission. Its underlying layer uses ssh for data transmission. And it has the same authentication mechanism and the same security level as ssh. When u
