boost/boost_1_91_0/libs/process/doc/stdio.adoc

stdio

When using io with a subprocess, all three standard streams (stdin, stdout, stderr) get set for the child-process. The default setting is to inherit the parent process.

This feature meant to be flexible, which is why there is little checking on the arguments assigned to one of those streams.

Pipes

asio pipes can be used for io. When using in process_stdio they will get automatically connected and the other side will get assigned to the child process:

example/stdio.cpp:20-29

Unresolved directive in <stdin> - include::../example/stdio.cpp[tag=readable_pipe]

readable pipes can be assigned to out and err, while writable_pipes can be assigned to in.

FILE*

FILE* can also be used for either side; this allows the stdin, stderr, stdout macros to be used:

example/stdio.cpp:35-38

Unresolved directive in <stdin> - include::../example/stdio.cpp[tag=file]

nullptr

nullptr may be used to set a given stream to be opened on the null-device (/dev/null on posix, NUL on windows). This is used to ignore output or give only EOF as input.

example/stdio.cpp:43-46

Unresolved directive in <stdin> - include::../example/stdio.cpp[tag=null]

native_handle

A native handle can be used as well, which means an int on posix or a HANDLE on windows. Furthermore, any object that has a native_handle function which returns a valid type for a stdio stream.

E.g. a domain socket on linux.

example/stdio.cpp:52-57

Unresolved directive in <stdin> - include::../example/stdio.cpp[tag=native_handle]

popen

Additionally, process v2 provides a popen class. It starts a process and connects pipes for stdin and stdout, so that the popen object can be used as a stream.

example/stdio.cpp:63-66

Unresolved directive in <stdin> - include::../example/stdio.cpp[tag=popen]