[Linux Internals]: What happens when you type ‘ls -l’ command in the terminal?

• Terminal is nothing but a wrapper that runs shell (bash or ksh etc) and allows us to enter commands
• Shell breaks down the commands entered by parsing
• It checks for shell expansion ( ex: ls * ) [ Resource: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html ]
• It checks for aliases for that command
• Tries to find the location of the command by searching under $PATH
• If it finds, it executes it!
• During the execution, libraries required by the program are loaded into the memory at the run time; If you run “ltrace or strace” on the command you can see library calls like mmap() [strace for system calls / ltrace for library calls]. Loading of libraries can happen through dynamic loading or static loading. Shell will use system calls to load these libraries while running the command.

Execution of program :

Interesting resources:

• https://sysadvent.blogspot.com/2010/12/day-15-down-ls-rabbit-hole.html