What is/dev/null in Linux?
/dev/null is a null device–a special type of virtual device. It is present in every Linux system, and the purpose of this device is to discard anything sent to it and read the End of File (EOF). Most virtual devices are used to read data; however, /dev/null is unique since it is used to suppress any data written to it.
What does 2>/dev/null do?
What exactly does 2>/dev/null do? Whether you are a new Linux user or an experienced bash programmer, it is highly probable that you encountered the cryptic command 2>/dev/null. Although this command looks technically complex, its purpose is very simple. It refers to a null device that is used to suppress outputs of various commands.
What does 2>&1 and/dev/null mean?
Then sometimes you find 2>&1, that means redirecting stderr to stdout. '/dev/null' essentially means "into the void", discarded. The 2 you mention refers to error output, where it should be directed. A redirection is not a pipe.
What happens when you write to/dev/null?
However, unlike most other virtual files, instead of reading, it’s used to write. Whatever you write to /dev/null will be discarded, forgotten into the void. It’s known as the null device in a UNIX system. Why would you want to discard something into the void? Let’s check out what /dev/null is and its usage.
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What is 2 Dev Null in shell script?
Specifying 2>/dev/null will filter out the errors so that they will not be output to your console. In more detail: 2 represents the error descriptor, which is where errors are written to. By default they are printed out on the console. /dev/null is the standard Linux device where you send output that you want ignored.
What does this mean Dev null 2 >& 1?
With 2>&1 , we are redirecting standard error output (file descriptor of 2 ) to standard output (file descriptor of 1 ) which gets written to /dev/null . The >& symbol is redirecting standard error output to standard output. The symbol & in 2>&1 implies that 1 is a destination file descriptor.
What is >& 2 in shell script?
and >&2 means send the output to STDERR, So it will print the message as an error on the console. You can understand more about shell redirecting from those references: https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Redirections.
What does 2 >& 1 at the end of a command do?
The left side of 2>&1 tells you what will be redirected, and the right side tells you where to. The & is used on the right side to distinguish stdout (1) or stderr (2) from files named 1 or 2 . So, 2>1 would end up creating a new file (if it doesn't exist already) named 1 and dump the stderr result in there.
What is Dev Null 2 Dev Null?
Whether you are a new Linux user or an experienced bash programmer, it is highly probable that you encountered the cryptic command 2>/dev/null. Although this command looks technically complex, its purpose is very simple. It refers to a null device that is used to suppress outputs of various commands.
What does the 2 >& 1 at the end of the following command mean LS names 2 >& 1?
It means redirect the output of stderr (file descriptor 2) to stdout (file descriptor 1).
What does 2 >& 1 mean in shell script?
1 "Standard output" output file descriptor. The expression 2>&1 copies file descriptor 1 to location 2 , so any output written to 2 ("standard error") in the execution environment goes to the same file originally described by 1 ("standard output").
What is dev Null in Linux?
/dev/null in Linux is a null device file. This will discard anything written to it, and will return EOF on reading. This is a command-line hack that acts as a vacuum, that sucks anything thrown to it.
What does 1 & 2 mean in shell script?
"You use &1 to reference the value of the file descriptor 1 (stdout). So when you use 2>&1 you are basically saying “Redirect the stderr to the same place we are redirecting the stdout”.
What means Dev Null?
/dev/null essentially means "into the void", discarded. The 2 you mention refers to error output, where it should be directed.
What is the use of n >& M command?
A command normally reads its input from the standard input, which happens to be your terminal by default. Similarly, a command normally writes its output to standard output, which is again your terminal by default....Redirection Commands.Sr.No.Command & Description7n <& m Merges input from stream n with stream m8 more rows
What does &> mean in Linux?
& means both standard output ( 1> ) and standard error( 2> ). >> means append to end of the file.
What is a null file?
It’s a special file that’s present in every single Linux system. However, unlike most other virtual files, instead of reading, it’s used to write. Whatever you write to /dev/null will be discarded, forgotten into the void. It’s known as the null device in a UNIX system.
Is Linux a virtual operating system?
by Sidratul Muntaha. Linux is an interesting operating system that hosts some virtual devices for numerous purposes. As far as programs running in the system are concerned, these virtual devices act as if they are real files. Tools can request and feed data from these sources.
Null Device – ‘/Dev/Null’
- All Linux-based systems have a feature called virtual devices. These virtual devices interact like actual files in the operating system. The working of such virtual devices is similar to real devices; they are used to write and read data. The main difference between the two is that the data for th…
File Descriptor – ‘2’
- Every command execution in Linux generates three associated files: standard input, standard output, and standard error files. The Linux operating system refers to each of these files with a unique non-negative integer. 1. ‘0’ for standard input 2. ‘1’ for standard output 3. ‘2’ for standard error The technical terms for standard input, standard output, and standard error streams are st…
File Redirection Operator – ‘>’
- The ‘>’ symbol is known as the file redirection operator. Its purpose is to direct what is to its left to the commands on the right side. In simpler words, any string of data to the left will be directed to the right side of the operator. So far, we have understood the purpose behind each component of the 2>/dev/null command. It sends the error stream to /dev/null, which discards it. In other word…
Conclusion
- We have dissected the 2>/dev/null command and simple examples in this article, and hopefully, now you understand what each bit of it does. However, this is just the tip of the iceberg; null devices are used in a multitude of ways in bash programming. Some of the more advanced uses include checking file existence, automating package installations, and avoiding scripts from run…