problem with getting correct pid in tcsh shell

In the tcsh shell, you can encounter issues when trying to retrieve the correct process ID (PID) due to the way tcsh handles its internal job control. Here are a few points to consider:

1. tcsh Backgrounding and Job Control: tcsh uses a job control system where backgrounded processes are assigned job IDs (JIDs) instead of individual PIDs. The $$ variable in tcsh refers to the shell's PID, not the specific process running in the background.

2. Use $! for Background Process PID: To get the PID of the most recently backgrounded process, you can use the $! variable in tcsh. It contains the PID of the last background process created in the shell. For example:

   tcshCopy code
   command &    # Run the command in the background
   
   set pid = $!  # Get the PID of the background process
   
   

3. Tracking Background Process PIDs: If you need to track multiple background processes and their PIDs, you may need to implement your own mechanism. For example, you can store the PIDs in an array or a file for later reference. Here's an example using an array:

   tcshCopy code
   set bg_pids = ()          # Initialize an empty array for storing PIDs
   
   
   
   command1 &                # Run command1 in the background
   
   set pid1 = $!             # Get the PID of command1
   
   set bg_pids = ($bg_pids $pid1)  # Store PID in the array
   
   
   
   command2 &                # Run command2 in the background
   
   set pid2 = $!             # Get the PID of command2
   
   set bg_pids = ($bg_pids $pid2)  # Store PID in the array
   
   
   
   # Access the PIDs from the array
   
   echo $bg_pids[1]          # Retrieve the first PID
   
   echo $bg_pids[2]          # Retrieve the second PID
   
   

Remember that tcsh is not as widely used as other shells like Bash, and it has certain limitations and quirks. If you require more advanced process management and PID handling, you may consider using a different shell that provides more robust features in this area.