Fix me: To be continued
Redirection makes it possible to control where the output of a command goes to, and where the input of a command comes from. It's a mighty tool that, together with pipelines, makes the shell powerful. The redirection operators are checked whenever a simple command is about to be executed.
I know how to redirect output and how to suppress them in bash. Now, suppose I accidentally forgot to append the output redirection part to the command (e.g. 2>&1 or > /tmp/mystdout) and my background process is already running for a while, can I still change to where stdout and stderr are being written to?
Using the top command with redirection works fine:
top > top.log
Now I want to use grep to filter a certain line:
top | grep "my_program" > top.log
But the log file will remain empty. But grep delivers an output when using
top | grep "my_program"
Where my_program has to be replaced by a running program to see some output.
Why does my approach not work ? And how can I fix it ?
I came across and unexpected behavior with redirections in tcsh.
Is there a way in Windows 7 cmd shell to redirect the stderr to stdout while keeping the stderr stream intact?
For example, I have a program that outputs to stderr and stdout the following message
TO STDOUT
TO STDERR
I want to have two files stderr.txt and stdout.txt with the following content
stderr.txt
TO STDERR
stdout.txt
TO STDOUT
TO STDERR
Is this possible?
I know of several questions that are asked. I want to know because you can redirect the output of a command to cd.
Simple Example
> echo $HOME | cd (not work)
> echo $HOME | xargs cd (not work)
I know I can do this
> cd $(echo $HOME) (work)
I want to know because you can not do redirection to cd command and if there are other commands that do not allow redirection.
I've never really thought about how the shell actually executes piped commands. I've always been told that the "stdout of one program gets piped into the stdin of another," as a way of thinking about pipes. So naturally, I thought that in the case of say, A | B, A would run first, then B gets the stdout of A, and uses the stdout of A as its input.
I'm paranoid about this, but hopefully it's a simple question:
Is there any difference between
cat file1 | egrep -oP "[Mm]y string" > /home/user/file.txt
and
cat file1|egrep -oP "[Mm]y string">/home/user/file.txt
i.e., does it matter if I have spaces padding the pipe (|) and redirection (>) characters?
I am struck up with a problem and that is with output redirection.
I used all the ways for the redirection of the output of c binary to a file, still it is failing.
Here are the different ways which I have used:
./a.out | tee -a /root/tmp.txt 2>&1
./a.out | tee -a /root/tmp.txt 1>&1
./a.out | tee -a /root/tmp.txt 2>&1 &
./a.out > /root/tmp.txt 2>&1 &
The issu
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