How does the exec command differ from executing commands through a shell in Unix-like systems?

The exec command in Unix-like systems replaces the current process with a new process, running the specified command without creating a new child process. Unlike the usual execution of commands through a shell, where a new process is created (fork + exec), exec replaces the current process, and after its invocation, the original process ceases to exist.

Main differences:

• exec does not create a new process but replaces the current one.
• After calling exec, the code of the original process does not continue to execute.
• It is used when you need to replace the process without creating an additional level of nesting.

Example:

# Normal command execution
ls
# A new process is created for ls, and after it finishes, control returns to the shell

# Using exec
exec ls
# The current shell process is replaced with ls, and after ls finishes, the process ends, the shell does not return

Thus, exec is useful for saving resources and managing processes when there is no need to return to the original process.