The word time is one of the bash shell reserved words. It is not a bash shell builtin. $ builtin time bash: builtin: time: not a shell builtin Bash does support the older Bourne shell keyword times as a builtin. This builtin prints out the user and system times used by the shell and its children. So where is the time reserved word used in the bash shell? It is primarily intended for printing pipeline timing statistics. From the current online bash documentation: The format for a pipeline is [time [-p]] [!] command1 [| command2 …] The output of each
The Bash shell hash builtin maintains a hash cache (table) containing the full pathname of previously executed commands that are on your PATH environmental variable. If the command is in the hash table, it just executes it without searching for it in the various path components. SYNTAX hash [-r] [-p filename] [name] OPTIONS -r Reset (causes the shell to forget all remembered locations) -p Use filename as the location of name (don’t search $PATH) If no arguments are given, information about remembered commands is printed. The return status is zero unless a name is not found or an invalid option
This post demonstrates how to write a loadable stat builtin for Korn shell 93.
This post discusses the undocumented alarm builtin in Korn Shell 93.