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Full Discussion: Blocking file read
Top Forums Programming Blocking file read Post 302078503 by cubathy on Saturday 1st of July 2006 07:46:02 AM
Old 07-01-2006
Blocking file read
There are many processes writing to log files at random times (they are all programmed in different manners and can not be altered). I am writing a new c program which should read from the log files whenever they are updated. At the moment it is just spooling, waiting for a change in file size, but I really want to block until an update is made on one of the files.
Can this be done?
I thought select or poll might work but apparently they arent much use when your using regular files.
Also looked at using fifo's but seeing as I cant alter the original code it seems impossible.

Any ideas?

thanks
 

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LEARN ABOUT OSF1

log

log(8)							      System Manager's Manual							    log(8)

NAME

       log - Records input and output from a program

SYNOPSIS

       /usr/sbin/log <logfile> <command>

OPERANDS

       The file in which to record the interaction being logged.  The command to execute.

DESCRIPTION

       The  log  program  runs <command> and logs the input to and output from <command> to the <logfile> file.  Input and output are logged until
       <command> exits, the log program exits, and the exit status of <command> is returned.

       The log program is used by the system  installation  procedure  and  the  it(8)	command  to  create  the  /var/adm/smlogs/install.log  and
       /var/adm/smlogs/it.log installation log files.

RESTRICTIONS

       Because	the  log  program is used in the installation standalone environment, program size was the greatest concern in its implementation.
       The log program does not search for the PATH variable to locate <command> and error messages are terse.

       The log program causes <command> to take standard input from and write standard output and standard error to  UNIX  pipes.   Some  commands
       will  not  be able to operate in this environment; therefore, it is suggested that you use the script(1) command instead.  UNIX shells will
       not issue prompts when run from log unless the shell is started with an explicit interactive switch (-i for most shells).  For example, log
       foo.tmp /sbin/sh -i

       In the previous example, foo.tmp is the name of <logfile>.

       The  log  program  intercepts  end-of-file (usually Ctrl/d).  Therefore programs which normally receive end-of-file as an exit command must
       exit by some other means.

ERRORS

       Log open error

   Explanation:
       The log program was unable to open <logfile>. Verify that the directory exists and that ownerships and permissions are set correctly.

       Exec Error

   Explanation:
       The log program was unable to execute <command>. Verify that you specified a full pathname for <command> and  that  <command>  is  an  exe-
       cutable file.

       Fork Error

   Explanation:
       The log program was unable to create one of the processes it requires to log data.

SEE ALSO

       Commands: it(8), script(1)

																	    log(8)
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