When I read a script of makefile, I meet with the following linux script command:
mv obj/*.o . 2>/dev/null
What does this command mean? I understand mv obj/*.o . means that all the files with suffix o in the obj folder will be moved to the current folder. What does 2> mean? When they are combined together, what is purpose? Thanks!
You're looking at output redirection (Bash). 2 stands for 'stderr', the error output. By redirecting it to /dev/null, you're discarding it to oblivion. Regular output, 'stdout' or 1 is still shown (in your terminal by default), though.
Basically, this is just silencing error output of the mv command.
A snippet from the above link explains it more general:
COMMAND_OUTPUT >
# Redirect stdout to a file.
# Creates the file if not present, otherwise overwrites it.
ls -lR > dir-tree.list
# Creates a file containing a listing of the directory tree.
[..]
1>filename
# Redirect stdout to file "filename."
1>>filename
# Redirect and append stdout to file "filename."
2>filename
# Redirect stderr to file "filename."
2>>filename
# Redirect and append stderr to file "filename."
&>filename
# Redirect both stdout and stderr to file "filename."
