|GNU Bash Reference Manual|
by Chet Ramey and Brian Fox
Paperback (6"x9"), 180 pages
RRP £19.95 ($29.95)
"An essential resource .... the most detailed coverage available for all aspects of Bash" --- Linux User and Developer Magazine (Issue 37, Mar 2004) Get a printed copy>>>
3.7.2 Command Search and Execution
After a command has been split into words, if it results in a simple command and an optional list of arguments, the following actions are taken.
- If the command name contains no slashes, the shell attempts to locate it. If there exists a shell function by that name, that function is invoked as described in section 3.3 Shell Functions.
- If the name does not match a function, the shell searches for it in the list of shell builtins. If a match is found, that builtin is invoked.
If the name is neither a shell function nor a builtin,
and contains no slashes, Bash searches each element of
$PATHfor a directory containing an executable file by that name. Bash uses a hash table to remember the full pathnames of executable files to avoid multiple
PATHsearches (see the description of
hashin section 4.1 Bourne Shell Builtins). A full search of the directories in
$PATHis performed only if the command is not found in the hash table. If the search is unsuccessful, the shell prints an error message and returns an exit status of 127.
- If the search is successful, or if the command name contains one or more slashes, the shell executes the named program in a separate execution environment. Argument 0 is set to the name given, and the remaining arguments to the command are set to the arguments supplied, if any.
- If this execution fails because the file is not in executable format, and the file is not a directory, it is assumed to be a shell script and the shell executes it as described in section 3.8 Shell Scripts.
- If the command was not begun asynchronously, the shell waits for the command to complete and collects its exit status.
|ISBN 0954161777||GNU Bash Reference Manual||See the print edition|