emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

lpr: add more accurate comments

Browse Source 
*: trailing whitespace removal
This commit is contained in:
Denis Vlasenko
2008-03-24 02:05:58 +00:00
parent 39c77c3738
commit 42cc304e90
10 changed files with 35 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
printutils/lpd.c
View File

@@ -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/
* <queue1>
* ...
* <queueN>
*
*
* <queueX> 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