What is the meaning of 2 and 1 in Unix?
The standard ones are 0 for standard input, 1 for standard output or 2 for standard error. Accordingly, what is the meaning of 2 &1 in Unix? 2>&1 means that STDERR redirects to the target of STDOUT (which is the file dirlist) We are redirecting error output to standard output which in turn is being re-directed to file dirlist.
What is the difference between command1 and command2 in Unix?
command1 && command2 executes command2 if (and only if) command1 execution ends up successfully. In Unix jargon, that means exit code / return code equal to zero. command1; command2 executes command2 after executing command1, sequentially. It does not matter whether the commands were successful or not. Show activity on this post.
What does 2>&1 mean in Linux?
The numbers refer to the file descriptors (fd). 2>&1 redirects fd 2 to 1. This works for any number of file descriptors if the program uses them. You can look at /usr/include/unistd.h if you forget them:
What is the meaning of the string&1 in the output?
&1 is used to reference the value of the file descriptor 1 (stdout). both Standard output (stdout) and Standard Error (stderr) will redirected to output.txt. Show activity on this post. 2 is the console standard error. 1 is the console standard output. This is the standard Unix, and Windows also follows the POSIX.
What does 2 >> mean in Unix?
(other special file descriptors include 0 for standard input and 1 for standard output). 2> /dev/null means to redirect standard error to /dev/null . /dev/null is a special device that discards everything that is written to it.
What is the meaning of 2 &1 in Linux?
2>&1 means redirect the stderr ( >2 ) to where stdout is being redirected to ( &1 ). Before we start, I want to go over a basic concept of file descriptors. There are 3 file descriptors in UNIX and each is associated with a number: Name.
What does 2 >> mean in a script?
1>> and 2>> are redirections for specific file-descriptors, in this case the standard output (file descriptor 1) and standard error (file descriptor 2).
What does 2 >& 1 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”. And that's why we can do something like this to redirect both stdout and stderr to the same place:"
What does >/ dev null 2 >& 1 mean?
/dev/null is a special filesystem object that discards everything written into it. Redirecting a stream into it means hiding your program's output. The 2>&1 part means "redirect the error stream into the output stream", so when you redirect the output stream, error stream gets redirected as well.
What does &> mean in bash?
>name means 1>name -- redirect stdout to the file name. &>name is like 1>name 2>name -- redirect stdout and stderr to the file name (however name is only opened once; if you actually wrote 1>name 2>name it'd try to open name twice and perhaps malfunction).
What is 2 and1 batch file?
The 1 denotes standard output (stdout). The 2 denotes standard error (stderr). So 2>&1 says to send standard error to where ever standard output is being redirected as well.
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 dev Null mean in Linux?
After executing the ping command, '>/dev/null' tells the system to suppress the output, and '2>&1' directs the standard error stream to standard output. In this way, all output of the command is discarded.
Linux tmp Directory: What is the Purpose?
The /tmp directory contains all the required files that are going to be required “temporarily” during program execution. In case of any crash or unexpected event, you can retrieve your file from the directory. Also, you can see which sub-programs are being used during the execution of a program.
Can This Directory Be Filled Up?
For a normal Linux user, it is really hard to fill the tmp directory up. The files that are stored in the tmp directory are really small, some kilobytes in size. So you have to have a gigantic amount of files gathered there to fill the directory. It is not impossible but is really hard.
Emptying the tmp Directory Mannually
As an average Linux user, it is not recommended to empty this tmp directory manually. That will lead to a system crash because the files stored inside it are necessary to run the programs that are opened right now.
What If I Delete the tmp Directory Accidentally?
Restoring the tmp directory is often needed because many Linux users delete the whole directory by accident. The restoring process is not a tough task at all. Execute the following commands stated below:
Conclusion
We have discussed a lot about the tmp directory in Linux here. Keeping these points in mind will be sufficient for any user to run a Linux system with ease.
