Redirecting to dev/null

[munna_dude]

hi all
what is the meaning of this.
2> /dev/null
can u please explain.

thank you in advance

[Franklin52]

Have a read of this:

http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_08_02.html#sect_08_02_03

Regards

[munna_dude]

Have a read of this:

http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_08_02.html#sect_08_02_03

Regards

yeah!
/dev/null -> errors will not print in the terminal and it redirect to null.
ok
but, why we use "2>", especially "2".

and can i use "2> /dev/null" in my program(it is big program).
is there any effect to my source.(program).

thank you in advance

[the_unforgiven]

2 is the stderr file descriptor.

[munna_dude]

2 is the stderr file descriptor.

can i use this in my program.
tell me if there is any effects.

thank you in adavnce

[Franklin52]

It's mostly used with the system- or popen functions.
On what case do you want to use that in your C program?

Regards

[munna_dude]

It's mostly used with the system- or popen functions.
On what case do you want to use that in your C program?

Regards

while running my exe(excuted file)
for ex:
linux.c is my file and compile like this
cc linux.c -o linux
and run it in the terminal
./linux 2> /dev/null

can i do like this

help me

thank you in avdvance

[Franklin52]

That means that an error message from your program, you write with these functions, goes to /dev/null:

perror("Error!");
fprintf(stderr, "%s: %s\n", "Error: ", "error message");

Regards

[the_unforgiven]

When a process is started by the kernel, it opens 3 file descriptors by default for every process:
o. 0 -> stdin (mapped to keyboard)
o. 1 -> stdout (mapped to the monitor/console/terminal)
o. 2 -> stderr (mapping same as stdout)

Conventionally, good programming practice says that all the error messages by any program should be output to stderr (i.e. fd = 2) - that's what the standard functions like perror() do.

This is because, if you want to capture only the error messages separately, the stderr file descriptor can be redirected to a file while normal output keeps coming to stdout fd - this way you get more control over how to handle the messages.

If you expect some error messages to be dumped by a program even in normal cases and want to just send them to trash, you use "2> /dev/null" construct.

HTH