Review changes on the grep_pipe function

Just renaming and unification with the grep command.

aexpect/ops_linux.py

@@ -432,22 +432,22 @@ def grep(session, expr, path, check=False, flags="-a"):
     return output
 
 
-def grep_pipe(session, cmd, pattern, flags = "", check = False):
+def grep_pipe(session, cmd, expr, check = False, flags ="-a"):
     """
     Invoke ``grep`` remotely searching for an expression in a command output.
 
-    :param session: vm session
+    :param session: session to run the command on
     :type session: ShellSession
-    :param str cmd: command that its output will be grepped
-    :param str pattern: pattern to grep
-    :param str flags: extra flags passed to ``grep`` on the command line
+    :param str cmd: command whose output will be grepped
+    :param str expr: search expression
     :param bool check: whether to quietly run grep for a boolean check
+    :param str flags: extra flags passed to ``grep`` on the command line
     :returns: whether there is a match or not or what ``grep`` emits on stdout
               if the check mode is disabled
     :rtype: bool or str
     :raises: ShellCmdError if the check mode is disabled and status is nonzero
     """
-    grep_command = f"{cmd} | grep {flags} '{pattern}'"
+    grep_command = f"{cmd} | grep {flags} '{expr}'"
     status, output = session.cmd_status_output(grep_command)
     if check:
         return status == 0