From 42cc304e9084843ad6b153afaf4b3f6c6528c364 Mon Sep 17 00:00:00 2001 From: Denis Vlasenko Date: Mon, 24 Mar 2008 02:05:58 +0000 Subject: lpr: add more accurate comments *: trailing whitespace removal --- printutils/lpd.c | 45 ++++++++++++++++++++++++++------------------- 1 file changed, 26 insertions(+), 19 deletions(-) (limited to 'printutils/lpd.c') diff --git a/printutils/lpd.c b/printutils/lpd.c index cac881383..bc0348eba 100644 --- a/printutils/lpd.c +++ b/printutils/lpd.c @@ -10,37 +10,40 @@ /* * A typical usage of BB lpd looks as follows: * # tcpsvd -E 0 515 lpd SPOOLDIR [HELPER-PROG [ARGS...]] - * - * This means a network listener is started on port 515 (default for LP protocol). + * + * This means a network listener is started on port 515 (default for LP protocol). * When a client connection is made (via lpr) lpd first change its working directory to SPOOLDIR. - * - * SPOOLDIR is the spool directory which contains printing queues + * + * SPOOLDIR is the spool directory which contains printing queues * and should have the following structure: - * + * * SPOOLDIR/ * * ... * - * + * * can be of two types: * A. a printer character device or an ordinary file a link to such; * B. a directory. - * - * In case A lpd just dumps the data it receives from client (lpr) to the + * + * In case A lpd just dumps the data it receives from client (lpr) to the * end of queue file/device. This is non-spooling mode. - * - * In case B lpd enters spooling mode. It reliably saves client data along with control info - * in two unique files under the queue directory. These files are named dfAXXXHHHH and cfAXXXHHHH, - * where XXX is the job number and HHHH is the client hostname. Unless a printing helper application + * + * In case B lpd enters spooling mode. It reliably saves client data along with control info + * in two unique files under the queue directory. These files are named dfAXXXHHHH and cfAXXXHHHH, + * where XXX is the job number and HHHH is the client hostname. Unless a printing helper application * is specified lpd is done at this point. - * + * + * NB: file names are produced by peer! They actually may be anything at all! + * lpd only sanitizes them (by removing most non-alphanumerics). + * * If HELPER-PROG (with optional arguments) is specified then lpd continues to process client data: - * 1. it reads and parses control file (cfA...). The parse process results in setting environment - * variables whose values were passed in control file; when parsing is complete, lpd deletes + * 1. it reads and parses control file (cfA...). The parse process results in setting environment + * variables whose values were passed in control file; when parsing is complete, lpd deletes * control file. - * 2. it spawns specified helper application. It is then the helper application who is responsible + * 2. it spawns specified helper application. It is then the helper application who is responsible * for both actual printing and deleting processed data file. - * + * * A good lpr passes control files which when parsed provide the following variables: * $H = host which issues the job * $P = user who prints @@ -49,13 +52,17 @@ * $L = print banner page * $M = the user to whom a mail should be sent if a problem occurs * $l = name of datafile ("dfAxxx") - file whose content are to be printed - * + * + * lpd also provides $DATAFILE environment variable - the ACTUAL name + * of the datafile under which it was saved. + * $l is not reliable (you are at mercy of remote peer), DON'T USE IT. + * * Thus, a typical helper can be something like this: * #!/bin/sh * cat "$l" >/dev/lp0 * mv -f "$l" save/ - * */ + #include "libbb.h" // strip argument of bad chars -- cgit v1.2.3