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How do I use a cat dev Null file?
You write to /dev/null every time you use it in a command such as touch file 2> /dev/null. You read from /dev/null every time you empty an existing file using a command such as cat /dev/null > bigfile or just > bigfile. Because of the file’s nature, you can’t change it in any way; you can only use it.
Is dev Null a text 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.
Why is dev Null used?
Usage. The null device is typically used for disposing of unwanted output streams of a process, or as a convenient empty file for input streams. This is usually done by redirection. The /dev/null device is a special file, not a directory, so one cannot move a whole file or directory into it with the Unix mv command.
How do you null a file?
log in the following examples.
- Empty File Content by Redirecting to Null.
- Empty File Using ‘true’ Command Redirection.
- Empty File Using cat/cp/dd utilities with /dev/null.
- Empty File Using echo Command.
- Empty File Using truncate Command.
What is the meaning of cat / dev / null?
The command will output the data from device /dev/null to the given file (mailbox of the root account). Since /dev/null responds just with end-of-file when reading from it nothing will be written to the file, but with the redirection > the shell will have cleared the file already. Actually this is equivalent to writing just
How can I clear multiple files by Cat / dev / null?
A good way to clear logs (syslog has a handle on file) which have frozen my linux server (out of space) I tried cat /dev/null > fileABC; cat /dev/null/ > fileXYZ How can I clear multiple files by cat /dev/null to multiple files in an efficient or single command.
What does / dev / null mean in a shell script?
/dev/null is a simple device (implemented in software and not corresponding to any hardware device on the system). /dev/null looks empty when you read from it. Writing to /dev/null does nothing: data written to this device simply “disappear.”.
Why does cat / dev / null Empty my log file?
Note that restarting the writing process won’t “recover” the space as the file will stay “holey”. If you really want the reported file size to be zeroed, you need to stop (kill) the writing process before blanking the file. This only made cat read /dev/null and immediately read file_log.txt and output the result to stdout, your screen.