Introduce trivial new pager.c helper infrastructure
This introduces the new function
void setup_pager(void);
to set up output to be written through a pager applocation.
All in preparation for doing the simple scripts in C.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/pager.c b/pager.c
new file mode 100644
index 0000000..1364e15
--- /dev/null
+++ b/pager.c
@@ -0,0 +1,48 @@
+#include "cache.h"
+
+/*
+ * This is split up from the rest of git so that we might do
+ * something different on Windows, for example.
+ */
+
+static void run_pager(void)
+{
+ const char *prog = getenv("PAGER");
+ if (!prog)
+ prog = "less";
+ setenv("LESS", "-S", 0);
+ execlp(prog, prog, NULL);
+}
+
+void setup_pager(void)
+{
+ pid_t pid;
+ int fd[2];
+
+ if (!isatty(1))
+ return;
+ if (pipe(fd) < 0)
+ return;
+ pid = fork();
+ if (pid < 0) {
+ close(fd[0]);
+ close(fd[1]);
+ return;
+ }
+
+ /* return in the child */
+ if (!pid) {
+ dup2(fd[1], 1);
+ close(fd[0]);
+ close(fd[1]);
+ return;
+ }
+
+ /* The original process turns into the PAGER */
+ dup2(fd[0], 0);
+ close(fd[0]);
+ close(fd[1]);
+
+ run_pager();
+ exit(255);
+}
