which vs command -v

which

• External command, typically found at /usr/bin/which
• Searches for executables in directories listed in PATH
• Returns the absolute path of the first match found in PATH
• Returns an error message if the command is not found
• Not POSIX-compliant: behavior might vary across Unix-like systems
• Less reliable for use in shell scripts

command -v

• Shell built-in command (e.g., bash, zsh)
• Searches for executables, shell built-ins, shell functions, and aliases
• Returns the absolute path if the command is an executable
• Returns the command definition if it’s a shell built-in, function, or alias
• Returns nothing if the command is not found
• POSIX-compliant: more consistent behavior across Unix-like systems
• More reliable for use in shell scripts