LIBSPOOL(3) Impressario LIBSPOOL(3)LIBRARY DESCRIPTIONlibspool provides a C Language application programming interface (API) to
the UNIX printer spooling system. There are two common UNIX printer
spooling systems, System V and BSD. While both of these spooling systems
provide essentially the same capabilities, each has its own command set
and neither provides a C API. libspool provides a single API to both
spooling systems. Spooling functions provided by libspool include print
job submittal and cancel, print queue reading and control.
LIBRARY ACCESS
A program that calls libspool functions must include the spool.h header
file located in the /usr/include directory. In addition, the program must
link with the libspool.a library located in /usr/lib. The link line would
look like:
... -lspool ...
FUNCTIONS
Spooling System Selection
SLSetSpooler
SLGetSpooler
Printer Information
SLGetPrinterList
SLGetPrinterInfo
SLGetDefPrinterName
Option Management
SLGetPrinterSettings
SLSysVGetSpoolerOptions
SLSysVGetPrinterOptions
SLSysVSaveSpoolerOptions
SLSysVSavePrinterOptions
Print Job Handling
SLSubmitJob
SLSubmitJobFd
SLSubmitJobBuf
SLSubmitJobSimple
SLCancelJob
Printer Queue Information
SLGetQueue
Printer Queue Control
SLSetSpoolerState
SLGetSpoolerState
Execution Error Handling
SLPerror
SLGetSpoolerError
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LIBSPOOL(3) Impressario LIBSPOOL(3)ARCHITECTURE
Many of the libspool functions rely on the System V or BSD spooling
system shell-level commands to accomplish the actual spooling system
work. The architecture of the library is depicted below.
User Program
|
libspool
|
System V ___ BSD
Spooling Commands Spooling Commands
DEBUGGING
If the global variable SLdebug is set to a non-zero value, libspool will
print debugging information to standard error during execution. The
global SLdebug is declared in the header file spool.h.
SIGNAL HANDLING (SIGCLD)
A number of libspool functions spawn child processes to accomplish their
tasks. The child processes are executed in a blocking fashion whereby the
parent waits for the child to complete its processing. During the
execution of a child process, libspool explicitly ignores the SIGCLD
signal. Following execution of the child, the library restores the
original SIGCLD handling. The library uses the POSIX signal handling
function sigaction(2) to set the state of signal handling. Code that
links with libspool that must catch the SIGCLD signal should use the
POSIX signal handling functions to avoid conflicts between signal
handling mechanisms.
NETWORK OPERATIONS
Certain libspool functions obtain information about network printers by
executing remote commands. It may be impossible for libspool to obtain a
connection to the remote machine (remote machine is down, network is not
reachable, etc.). In this case the libspool function will timeout and
return an error code. The timeout period, in seconds, is specified by the
global variable SLnet_timeout. The default timeout period is specified by
the value of SL_NET_TIMEOUT in spool.h.
SEE ALSOlp(1), lpr(1), sigaction(2)
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