On CentOS 7.0.1406 I get differing output when runningps -A -o pid,command | grep [r]esquethan when I runps -A -o pid,comm | grep [r]esqueThe latter returns nothing; the former what I would expect. I was under the impression that comm was an alias for command. Could someone please explain the difference?  
ps - what is the difference between -o comm and -o command?
shell;centos
They are not aliases. Command outputs the full command and comm only the command name, so it is possible that the outputs are different. It all depends on what you want to extract the grep command.An example:$ ps -A -o pid,command | grep 9600376 /sbin/agetty --keep-baud 115200 38400 9600 ttyS0 vt220and the output for the following is empty:ps -A -o pid,comm | grep 9600The string 9600 is part of the complete command but the command name.command, and cmd are aliases to args, with prints the command with all its arguments as string. comm is a different sorting code that prints only the executable name. Manpage snippet:   args      COMMAND command with all its arguments as a string.   cmd       CMD    see args. (alias args, command).   comm      COMMAND command name (only the executable name).   command   COMMAND see args. (alias args, cmd).