Convenience functions that encapsulate a sequence of
start_command() followed by finish_command(). The argument argv
specifies the program and its arguments. The argument opt is zero
- or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`, or
- `RUN_COMMAND_STDOUT_TO_STDERR` that correspond to the members
- .no_stdin, .git_cmd, .stdout_to_stderr of `struct child_process`.
+ or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`,
+ `RUN_COMMAND_STDOUT_TO_STDERR`, or `RUN_SILENT_EXEC_FAILURE`
+ that correspond to the members .no_stdin, .git_cmd,
+ .stdout_to_stderr, .silent_exec_failure of `struct child_process`.
The argument dir corresponds the member .dir. The argument env
corresponds to the member .env.
+The functions above do the following:
+
+. If a system call failed, errno is set and -1 is returned. A diagnostic
+ is printed.
+
+. If the program was not found, then -1 is returned and errno is set to
+ ENOENT; a diagnostic is printed only if .silent_exec_failure is 0.
+
+. Otherwise, the program is run. If it terminates regularly, its exit
+ code is returned. No diagnistic is printed, even if the exit code is
+ non-zero.
+
+. If the program terminated due to a signal, then the return value is the
+ signal number - 128, ie. it is negative and so indicates an unusual
+ condition; a diagnostic is printed. This return value can be passed to
+ exit(2), which will report the same code to the parent process that a
+ POSIX shell's $? would report for a program that died from the signal.
+
+
`start_async`::
Run a function asynchronously. Takes a pointer to a `struct
Wait for the completion of an asynchronous function that was
started with start_async().
+`run_hook`::
+
+ Run a hook.
+ The first argument is a pathname to an index file, or NULL
+ if the hook uses the default index file or no index is needed.
+ The second argument is the name of the hook.
+ The further arguments correspond to the hook arguments.
+ The last argument has to be NULL to terminate the arguments list.
+ If the hook does not exist or is not executable, the return
+ value will be zero.
+ If it is executable, the hook will be executed and the exit
+ status of the hook is returned.
+ On execution, .stdout_to_stderr and .no_stdin will be set.
+ (See below.)
+
Data structures
---------------
To specify a new initial working directory for the sub-process,
specify it in the .dir member.
+If the program cannot be found, the functions return -1 and set
+errno to ENOENT. Normally, an error message is printed, but if
+.silent_exec_failure is set to 1, no message is printed for this
+special error condition.
+
* `struct async`