I use tcsh (not csh), and ran pgrep csh | xargs ps -p to see why I appeared to be running csh. A portion of the results: 1529 pts/0    Ss     0:00 -csh 1764 pts/3    Ss     0:00 -tcsh 1979 pts/4    Ss+    0:00 -bin/tcshI then did ps -p 1529 1764 1979 and got the same thing:  PID TTY      STAT   TIME COMMAND 1529 pts/0    Ss     0:00 -csh 1764 pts/3    Ss     0:00 -tcsh 1979 pts/4    Ss+    0:00 -bin/tcshThen I did ps -p 1529; ps -p 1764; ps -p 1979  PID TTY          TIME CMD 1529 pts/0    00:00:00 tcsh  PID TTY          TIME CMD 1764 pts/3    00:00:00 tcsh  PID TTY          TIME CMD 1979 pts/4    00:00:00 tcshps --version gives procps-ng version 3.3.10 and tcsh --version yields tcsh 6.19.00 (Astron) 2015-05-21 (x86_64-unknown-linux) options wide,nls,dl,al,kan,sm,rh,color,filec.Why this odd behavior? I'm trying to write a process monitor, and having tcsh take three different forms is annoying.
Why does ps -p proc1 proc2 proc3 show -csh, -tcsh, and -/bin/tcsh, whereas ps -p proc[n] individually all say tcsh?
ps;tcsh;csh