274 lines
11 KiB
Text
274 lines
11 KiB
Text
@c -*- mode: texinfo -*-
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@deftypefn Extension {struct pex_obj *} pex_init (int @var{flags}, const char *@var{pname}, const char *@var{tempbase})
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Prepare to execute one or more programs, with standard output of each
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program fed to standard input of the next. This is a system
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independent interface to execute a pipeline.
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@var{flags} is a bitwise combination of the following:
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@table @code
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@vindex PEX_RECORD_TIMES
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@item PEX_RECORD_TIMES
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Record subprocess times if possible.
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@vindex PEX_USE_PIPES
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@item PEX_USE_PIPES
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Use pipes for communication between processes, if possible.
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@vindex PEX_SAVE_TEMPS
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@item PEX_SAVE_TEMPS
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Don't delete temporary files used for communication between
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processes.
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@end table
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@var{pname} is the name of program to be executed, used in error
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messages. @var{tempbase} is a base name to use for any required
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temporary files; it may be @code{NULL} to use a randomly chosen name.
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@end deftypefn
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@deftypefn Extension {const char *} pex_run (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{outname}, const char *@var{errname}, int *@var{err})
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Execute one program in a pipeline. On success this returns
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@code{NULL}. On failure it returns an error message, a statically
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allocated string.
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@var{obj} is returned by a previous call to @code{pex_init}.
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@var{flags} is a bitwise combination of the following:
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@table @code
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@vindex PEX_LAST
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@item PEX_LAST
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This must be set on the last program in the pipeline. In particular,
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it should be set when executing a single program. The standard output
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of the program will be sent to @var{outname}, or, if @var{outname} is
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@code{NULL}, to the standard output of the calling program. Do @emph{not}
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set this bit if you want to call @code{pex_read_output}
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(described below). After a call to @code{pex_run} with this bit set,
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@var{pex_run} may no longer be called with the same @var{obj}.
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@vindex PEX_SEARCH
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@item PEX_SEARCH
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Search for the program using the user's executable search path.
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@vindex PEX_SUFFIX
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@item PEX_SUFFIX
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@var{outname} is a suffix. See the description of @var{outname},
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below.
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@vindex PEX_STDERR_TO_STDOUT
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@item PEX_STDERR_TO_STDOUT
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Send the program's standard error to standard output, if possible.
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@vindex PEX_BINARY_INPUT
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@vindex PEX_BINARY_OUTPUT
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@item PEX_BINARY_INPUT
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@itemx PEX_BINARY_OUTPUT
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The standard input (output) of the program should be read (written) in
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binary mode rather than text mode. These flags are ignored on systems
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which do not distinguish binary mode and text mode, such as Unix. For
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proper behavior these flags should match appropriately---a call to
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@code{pex_run} using @code{PEX_BINARY_OUTPUT} should be followed by a
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call using @code{PEX_BINARY_INPUT}.
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@end table
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@var{executable} is the program to execute. @var{argv} is the set of
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arguments to pass to the program; normally @code{@var{argv}[0]} will
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be a copy of @var{executable}.
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@var{outname} is used to set the name of the file to use for standard
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output. There are two cases in which no output file will be used:
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@enumerate
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@item
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if @code{PEX_LAST} is not set in @var{flags}, and @code{PEX_USE_PIPES}
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was set in the call to @code{pex_init}, and the system supports pipes
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@item
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if @code{PEX_LAST} is set in @var{flags}, and @var{outname} is
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@code{NULL}
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@end enumerate
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@noindent
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Otherwise the code will use a file to hold standard
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output. If @code{PEX_LAST} is not set, this file is considered to be
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a temporary file, and it will be removed when no longer needed, unless
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@code{PEX_SAVE_TEMPS} was set in the call to @code{pex_init}.
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There are two cases to consider when setting the name of the file to
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hold standard output.
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@enumerate
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@item
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@code{PEX_SUFFIX} is set in @var{flags}. In this case
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@var{outname} may not be @code{NULL}. If the @var{tempbase} parameter
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to @code{pex_init} was not @code{NULL}, then the output file name is
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the concatenation of @var{tempbase} and @var{outname}. If
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@var{tempbase} was @code{NULL}, then the output file name is a random
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file name ending in @var{outname}.
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@item
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@code{PEX_SUFFIX} was not set in @var{flags}. In this
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case, if @var{outname} is not @code{NULL}, it is used as the output
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file name. If @var{outname} is @code{NULL}, and @var{tempbase} was
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not NULL, the output file name is randomly chosen using
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@var{tempbase}. Otherwise the output file name is chosen completely
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at random.
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@end enumerate
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@var{errname} is the file name to use for standard error output. If
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it is @code{NULL}, standard error is the same as the caller's.
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Otherwise, standard error is written to the named file.
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On an error return, the code sets @code{*@var{err}} to an @code{errno}
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value, or to 0 if there is no relevant @code{errno}.
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@end deftypefn
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@deftypefn Extension {const char *} pex_run_in_environment (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{executable}, char * const *@var{argv}, char * const *@var{env}, int @var{env_size}, const char *@var{outname}, const char *@var{errname}, int *@var{err})
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Execute one program in a pipeline, permitting the environment for the
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program to be specified. Behaviour and parameters not listed below are
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as for @code{pex_run}.
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@var{env} is the environment for the child process, specified as an array of
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character pointers. Each element of the array should point to a string of the
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form @code{VAR=VALUE}, with the exception of the last element that must be
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@code{NULL}.
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@end deftypefn
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@deftypefn Extension {FILE *} pex_input_file (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{in_name})
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Return a stream for a temporary file to pass to the first program in
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the pipeline as input.
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The name of the input file is chosen according to the same rules
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@code{pex_run} uses to choose output file names, based on
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@var{in_name}, @var{obj} and the @code{PEX_SUFFIX} bit in @var{flags}.
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Don't call @code{fclose} on the returned stream; the first call to
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@code{pex_run} closes it automatically.
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If @var{flags} includes @code{PEX_BINARY_OUTPUT}, open the stream in
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binary mode; otherwise, open it in the default mode. Including
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@code{PEX_BINARY_OUTPUT} in @var{flags} has no effect on Unix.
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@end deftypefn
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@deftypefn Extension {FILE *} pex_input_pipe (struct pex_obj *@var{obj}, int @var{binary})
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Return a stream @var{fp} for a pipe connected to the standard input of
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the first program in the pipeline; @var{fp} is opened for writing.
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You must have passed @code{PEX_USE_PIPES} to the @code{pex_init} call
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that returned @var{obj}.
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You must close @var{fp} using @code{fclose} yourself when you have
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finished writing data to the pipeline.
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The file descriptor underlying @var{fp} is marked not to be inherited
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by child processes.
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On systems that do not support pipes, this function returns
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@code{NULL}, and sets @code{errno} to @code{EINVAL}. If you would
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like to write code that is portable to all systems the @code{pex}
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functions support, consider using @code{pex_input_file} instead.
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There are two opportunities for deadlock using
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@code{pex_input_pipe}:
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@itemize @bullet
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@item
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Most systems' pipes can buffer only a fixed amount of data; a process
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that writes to a full pipe blocks. Thus, if you write to @file{fp}
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before starting the first process, you run the risk of blocking when
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there is no child process yet to read the data and allow you to
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continue. @code{pex_input_pipe} makes no promises about the
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size of the pipe's buffer, so if you need to write any data at all
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before starting the first process in the pipeline, consider using
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@code{pex_input_file} instead.
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@item
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Using @code{pex_input_pipe} and @code{pex_read_output} together
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may also cause deadlock. If the output pipe fills up, so that each
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program in the pipeline is waiting for the next to read more data, and
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you fill the input pipe by writing more data to @var{fp}, then there
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is no way to make progress: the only process that could read data from
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the output pipe is you, but you are blocked on the input pipe.
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@end itemize
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@end deftypefn
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@deftypefn Extension {FILE *} pex_read_output (struct pex_obj *@var{obj}, int @var{binary})
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Returns a @code{FILE} pointer which may be used to read the standard
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output of the last program in the pipeline. When this is used,
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@code{PEX_LAST} should not be used in a call to @code{pex_run}. After
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this is called, @code{pex_run} may no longer be called with the same
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@var{obj}. @var{binary} should be non-zero if the file should be
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opened in binary mode. Don't call @code{fclose} on the returned file;
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it will be closed by @code{pex_free}.
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@end deftypefn
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@deftypefn Extension int pex_get_status (struct pex_obj *@var{obj}, int @var{count}, int *@var{vector})
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Returns the exit status of all programs run using @var{obj}.
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@var{count} is the number of results expected. The results will be
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placed into @var{vector}. The results are in the order of the calls
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to @code{pex_run}. Returns 0 on error, 1 on success.
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@end deftypefn
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@deftypefn Extension int pex_get_times (struct pex_obj *@var{obj}, int @var{count}, struct pex_time *@var{vector})
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Returns the process execution times of all programs run using
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@var{obj}. @var{count} is the number of results expected. The
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results will be placed into @var{vector}. The results are in the
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order of the calls to @code{pex_run}. Returns 0 on error, 1 on
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success.
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@code{struct pex_time} has the following fields of the type
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@code{unsigned long}: @code{user_seconds},
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@code{user_microseconds}, @code{system_seconds},
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@code{system_microseconds}. On systems which do not support reporting
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process times, all the fields will be set to @code{0}.
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@end deftypefn
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@deftypefn Extension void pex_free (struct pex_obj @var{obj})
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Clean up and free all data associated with @var{obj}.
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@end deftypefn
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@deftypefn Extension {const char *} pex_one (int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{pname}, const char *@var{outname}, const char *@var{errname}, int *@var{status}, int *@var{err})
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An interface to permit the easy execution of a
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single program. The return value and most of the parameters are as
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for a call to @code{pex_run}. @var{flags} is restricted to a
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combination of @code{PEX_SEARCH}, @code{PEX_STDERR_TO_STDOUT}, and
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@code{PEX_BINARY_OUTPUT}. @var{outname} is interpreted as if
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@code{PEX_LAST} were set. On a successful return, @code{*@var{status}} will
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be set to the exit status of the program.
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@end deftypefn
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@deftypefn Extension int pexecute (const char *@var{program}, char * const *@var{argv}, const char *@var{this_pname}, const char *@var{temp_base}, char **@var{errmsg_fmt}, char **@var{errmsg_arg}, int @var{flags})
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This is the old interface to execute one or more programs. It is
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still supported for compatibility purposes, but is no longer
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documented.
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@end deftypefn
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@deftypefn Extension int pwait (int @var{pid}, int *@var{status}, int @var{flags})
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Another part of the old execution interface.
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@end deftypefn
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