Added libbe.pager

diff --git a/libbe/pager.py b/libbe/pager.py
new file mode 100644 (file)
index 0000000..8190b2a
--- /dev/null
+++ b/libbe/pager.py
@@ -0,0 +1,51 @@
+# Copyright
+
+"""
+Automatic pager for terminal output (a la Git).
+"""
+
+import sys, os, select
+
+# see http://nex-3.com/posts/73-git-style-automatic-paging-in-ruby
+def run_pager(paginate=None):
+    """
+    paginate should be one of 'never', 'auto', or 'always'.
+
+    usage: just call this function and continue using sys.stdout like
+    you normally would.
+    """
+    if paginate == 'never' \
+            or sys.platform == 'win32' \
+            or not hasattr(sys.stdout, 'isatty') \
+            or sys.stdout.isatty() == False:
+        return
+
+    if paginate == 'auto':
+        if 'LESS' not in os.environ:
+            os.environ['LESS'] = '' # += doesn't work on undefined var
+        # don't page if the input is short enough
+        os.environ['LESS'] += ' -FRX'
+    if 'PAGER' in os.environ:
+        pager = os.environ['PAGER']
+    else:
+        pager = 'less'
+
+    read_fd, write_fd = os.pipe()
+    if os.fork() == 0:
+        # child process
+        os.close(read_fd)
+        os.close(0)
+        os.dup2(write_fd, 1)
+        os.close(write_fd)
+        if hasattr(sys.stderr, 'isatty') and sys.stderr.isatty() == True:
+            os.dup2(1, 2)
+        return
+
+    # parent process, become pager
+    os.close(write_fd)
+    os.dup2(read_fd, 0)
+    os.close(read_fd)
+
+    # Wait until we have input before we start the pager
+    select.select([0], [], [])
+    os.execlp(pager, pager)