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Redirecting stdout and stderr to a file: The I/O streams can be redirected by putting the n> operator in use, where n is the file descriptor number. For redirecting stdout, we use “1>” and for stderr, “2>” is added as an operator.
Understanding the concept of redirections and file descriptors is very important when working on the command line. To redirect stderr and stdout , use the 2>&1 or &> constructs.
In Linux, for redirecting output to a file, utilize the ”>” and ”>>” redirection operators or the top command. Redirection allows you to save or redirect the output of a command in another file on your system. You can use it to save the outputs and use them later for different purposes.
I was running a program (valgrind, actually) on my Ubuntu machine, and had redirected both stdout and stderr to different files. I was surprised to see a short message appear on the screen -- how is that possible? How could I do that myself in a C++ program?
EDIT: Here's the command I used, and the output:
$ valgrind ./myprogram > val.out 2> val.err
*** stack smashing detected ***: ./myprogram terminated
EDIT2: Playing with it a little more, it turns out that myprogram, not valgrind, is causing the message to be printed, and as answered below, it looks like gcc stack smashing detection code is printing to /dev/tty
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