feat(process): fork/exec/id/session + system/popen

include/stdio.h

@@ -261,6 +261,21 @@ tmpfile(void);
 __attribute__((pure)) int
 fileno(FILE *stream);
 
+/*
+ * Run command in a subshell ("sh -c command") with a pipe attached to
+ * its standard output (mode "r") or standard input (mode "w"). Only the
+ * two POSIX modes are accepted (the glibc "re"/"we" close-on-exec
+ * extension is not). Returns the stream, or NULL with errno set.
+ * pclose closes the stream, waits for the shell, and returns its
+ * termination status (the raw wait status, e.g. 0 for "exit 0"), or -1
+ * when the stream was not opened by popen or the wait failed.
+ */
+FILE *
+popen(const char *command, const char *mode);
+
+int
+pclose(FILE *stream);
+
 /* getc/putc/getchar/putchar as macros over fgetc/fputc (see above). */
 #define getc(stream) fgetc(stream)
 #define putc(c, stream) fputc((c), (stream))