Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
How to redirect error message to a file
Answer:
Assume you have some program/script that print to the standard error stream (i.e. stderr)
E.g. error.pl
print STDERR 'error';
You cannot redirect the error message just by basic file redirection, e.g.
perl error.pl > error.txt
Instead, you need to use 2>
perl error.pl 2> error.txt
How to replace a character for a new line in vi?
Answer:
You might have tried
:%s/,/\n/g
But it didn't work.
Try replacing with \r instead
:%s/,/\r/g
Find the current user UID and GID
Answer:
Use the id command
E.g. check the UID and GID of the user - "mysql"
# id mysql
uid=106(mysql) gid=111(mysql) groups=111(mysql)
How to change the default runlevel?
Answer:
For example, you want to change the runlevel from GUI mode to console mode
Edit the file /etc/inittab, change the following line
id:5:initdefault
Change the number from 5 to 3.
For more information about runlevel, see: http://en.wikipedia.org/wiki/Runlevel
How to grep a string in a binary file?
Answer:
Assume you have a binary file "foo.bin", you can combine strings with the grep command.
strings foo.bin | grep bar
