X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=run-command.h;h=debe3074b5a01fb5a19e61f07ff66c250cdc4f82;hb=319a36a5c2da8dd07993caac43b7820bff3b0d37;hp=e9c84d03639a59178e16361ee70df95835b9beb3;hpb=e72ae28895b22052b7ca2eef36c039ac62671f7d;p=git.git

diff --git a/run-command.h b/run-command.h
index e9c84d036..debe3074b 100644
--- a/run-command.h
+++ b/run-command.h
@@ -14,6 +14,24 @@ enum {
 struct child_process {
 	const char **argv;
 	pid_t pid;
+	/*
+	 * Using .in, .out, .err:
+	 * - Specify 0 for no redirections (child inherits stdin, stdout,
+	 *   stderr from parent).
+	 * - Specify -1 to have a pipe allocated as follows:
+	 *     .in: returns the writable pipe end; parent writes to it,
+	 *          the readable pipe end becomes child's stdin
+	 *     .out, .err: returns the readable pipe end; parent reads from
+	 *          it, the writable pipe end becomes child's stdout/stderr
+	 *   The caller of start_command() must close the returned FDs
+	 *   after it has completed reading from/writing to it!
+	 * - Specify > 0 to set a channel to a particular FD as follows:
+	 *     .in: a readable FD, becomes child's stdin
+	 *     .out: a writable FD, becomes child's stdout/stderr
+	 *     .err > 0 not supported
+	 *   The specified FD is closed by start_command(), even in case
+	 *   of errors!
+	 */
 	int in;
 	int out;
 	int err;