Personally, my favorite (requires bash and other things that are standard on most Linux distributions) The details can depend a lot on what the two things output and how you want to merge them … Contents of command1 and command2 after each other in the output: cat <(command1) <(command2) > outputfile Or if both commands … Read more
You could always do this: ssh user@host ls -l /some/directory That will SSH to the host, run ls, dump the output back to you and immediately disconnect.
If you’re talking about the error message, you can suppress that by sending it to the bit bucket: cp ./src/*/*.h ./aaa 2>/dev/null If you want to suppress the exit code and the error message: cp ./src/*/*.h ./aaa 2>/dev/null || :
It’s not a good idea to edit /etc/profile for things like this, because you’ll lose all your changes whenever CentOS publishes an update for this file. This is exactly what /etc/profile.d is for: echo ‘pathmunge /usr/lib/ruby-enterprise/bin’ > /etc/profile.d/ree.sh chmod +x /etc/profile.d/ree.sh Log back in and enjoy your (safely) updated $PATH: echo $PATH /usr/lib/ruby-enterprise/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin which ruby … Read more
You can use the -s switch to su to run a particular shell su -s /bin/bash -c ‘/path/to/your/script’ testuser (Prepend sudo to the above if testuser is a passwordless user.)
A single hyphen can be followed by multiple single-character flags. A double hyphen prefixes a single, multicharacter option. Consider this example: tar -czf In this example, -czf specifies three single-character flags: c, z, and f. Now consider another example: tar –exclude In this case, –exclude specifies a single, multicharacter option named exclude. The double hyphen … Read more
To quickly kill all the stopped jobs under the bash, enter: kill -9 `jobs -ps` jobs -ps lists the process IDs (-p) of the stopped (-s) jobs. kill -9 `jobs -ps` sends SIGKILL signals to all of them.
Most likely your ls is aliased to ls –color=auto, which tells ls to only use colors when its output is a tty. If you do ls –color (which is morally equivalent to ls –color=always), that will force it to turn on colors. You could also change your alias to do that, but I wouldn’t really … Read more
You can pipe the script’s output through a loop that prefixes the current date and time: ./script.sh | while IFS= read -r line; do printf ‘%s %s\n’ “$(date)” “$line”; done >>/var/log/logfile If you’ll be using this a lot, it’s easy to make a bash function to handle the loop: adddate() { while IFS= read -r … Read more
set -e causes the shell to exit if any subcommand or pipeline returns a non-zero status. The answer the interviewer was probably looking for is: It would be dangerous to use “set -e” when creating init.d scripts: From http://www.debian.org/doc/debian-policy/ch-opersys.html 9.3.2 — Be careful of using set -e in init.d scripts. Writing correct init.d scripts requires … Read more