Pid is not a child of this shell

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When you encounter the error message “pid is not a child of this shell,” it usually means that the process ID (pid) you are referring to does not belong to the current shell session or is not a valid child process.

Let’s break down the error and explain it further:

  • PID (Process ID): In a Unix-like operating system, each process is assigned a unique numerical identifier called a PID. PIDs are used to track and manage processes dynamically.
  • Child Process: In the context of process management, a child process is a process created by another process (parent process). The parent process typically creates a child process to delegate certain tasks.
  • Shell: A shell is a command-line interpreter that provides an interface for users to interact with the operating system. It accepts commands from the user and executes them.

Now, let’s see an example to better understand the error:

# Assume the current shell has a process ID (PID) of 12345
$ ps -ef | grep 12345
  UID   PID  PPID   C STIME   TTY       TIME   CMD
  user 12345 67890  0  12:00  pts/0     00:00:00  process1.sh
$ kill 54321
  bash: kill: (54321) - No such process
$ kill 12345
  bash: kill: (12345) - Operation not permitted

In this example, we have a current shell with a PID of 12345. We execute the ps command to display the process information and filter it with the grep command to find the line containing the current shell’s PID.

The output shows that the parent process ID (PPID) of 12345 is 67890, indicating that the current shell is not the direct child of the main shell process (init).

When we attempt to use the kill command on a non-existent process (54321), we receive the error message “No such process.” This error occurs because the process with that PID does not exist.

Similarly, if we try to kill our own shell process (12345), we get the error message “Operation not permitted.” This error occurs because we are not allowed to terminate the current shell session from within itself.

To avoid this error, you need to ensure that the PID you are referencing belongs to a child process of the current shell or a process that your user has sufficient permissions to manage.

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