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Top Forums Shell Programming and Scripting Perl open(CMD, "cmd |"); buffering problem.. Post 302593140 by Shawn, Lee on Wednesday 25th of January 2012 08:11:37 PM
Old 01-25-2012
Perl open(CMD, "cmd |"); buffering problem..

Hello,

There's a third-party application's command that shows the application's status like "tail -f verybusy.log". When use the command, the output comes every 1-sec. but when it goes in a script below the output comes every 8-sec...What is the problem and how can I fix it?

Code:
open(CMD, "/appbin/command |");
while(<CMD>){
        print;
}
close(CMD);

Thanks,
 

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

NAME
sv - control and manage services monitored by runsv(8) SYNOPSIS
sv [-v] [-w sec] command services /etc/init.d/service [-w sec] command DESCRIPTION
The sv program reports the current status and controls the state of services monitored by the runsv(8) supervisor. services consists of one or more arguments, each argument naming a directory service used by runsv(8). If service doesn't start with a dot or slash and doesn't end with a slash, it is searched in the default services directory /etc/service/, otherwise relative to the current directory. command is one of up, down, status, once, pause, cont, hup, alarm, interrupt, 1, 2, term, kill, or exit, or start, stop, restart, shutdown, force-stop, force-reload, force-restart, force-shutdown. The sv program can be sym-linked to /etc/init.d/ to provide an LSB init script interface. The service to be controlled then is specified by the base name of the ``init script''. COMMANDS
status Report the current status of the service, and the appendant log service if available, to standard output. up If the service is not running, start it. If the service stops, restart it. down If the service is running, send it the TERM signal, and the CONT signal. If ./run exits, start ./finish if it exists. After it stops, do not restart service. once If the service is not running, start it. Do not restart it if it stops. pause cont hup alarm interrupt quit 1 2 term kill If the service is running, send it the STOP, CONT, HUP, ALRM, INT, QUIT, USR1, USR2, TERM, or KILL signal respectively. exit If the service is running, send it the TERM signal, and the CONT signal. Do not restart the service. If the service is down, and no log service exists, runsv(8) exits. If the service is down and a log service exists, send the TERM signal to the log service. If the log service is down, runsv(8) exits. This command is ignored if it is given to an appendant log service. sv actually looks only at the first character of these commands. Commands compatible to LSB init script actions status Same as status. start Same as up, but wait up to 7 seconds for the command to take effect. Then report the status or timeout. If the script ./check exists in the service directory, sv runs this script to check whether the service is up and available; it's considered to be avail- able if ./check exits with 0. stop Same as down, but wait up to 7 seconds for the service to become down. Then report the status or timeout. reload Same as hup, and additionally report the status afterwards. restart Send the commands term, cont, and up to the service, and wait up to 7 seconds for the service to restart. Then report the status or timeout. If the script ./check exists in the service directory, sv runs this script to check whether the service is up and avail- able again; it's considered to be available if ./check exits with 0. shutdown Same as exit, but wait up to 7 seconds for the runsv(8) process to terminate. Then report the status or timeout. force-stop Same as down, but wait up to 7 seconds for the service to become down. Then report the status, and on timeout send the service the kill command. force-reload Send the service the term and cont commands, and wait up to 7 seconds for the service to restart. Then report the status, and on timeout send the service the kill command. force-restart Send the service the term, cont and up commands, and wait up to 7 seconds for the service to restart. Then report the status, and on timeout send the service the kill command. If the script ./check exists in the service directory, sv runs this script to check whether the service is up and available again; it's considered to be available if ./check exits with 0. force-shutdown Same as exit, but wait up to 7 seconds for the runsv(8) process to terminate. Then report the status, and on timeout send the ser- vice the kill command. try-restart if the service is running, send it the term and cont commands, and wait up to 7 seconds for the service to restart. Then report the status or timeout. Additional Commands check Check for the service to be in the state that's been requested. Wait up to 7 seconds for the service to reach the requested state, then report the status or timeout. If the requested state of the service is up, and the script ./check exists in the service direc- tory, sv runs this script to check whether the service is up and running; it's considered to be up if ./check exits with 0. OPTIONS
-v If the command is up, down, term, once, cont, or exit, then wait up to 7 seconds for the command to take effect. Then report the status or timeout. -w sec Override the default timeout of 7 seconds with sec seconds. This option implies -v. ENVIRONMENT
SVDIR The environment variable $SVDIR overrides the default services directory /etc/service/. SVWAIT The environment variable $SVWAIT overrides the default 7 seconds to wait for a command to take effect. It is overridden by the -w option. EXIT CODES
sv exits 0, if the command was successfully sent to all services, and, if it was told to wait, the command has taken effect to all ser- vices. For each service that caused an error (e.g. the directory is not controlled by a runsv(8) process, or sv timed out while waiting), sv increases the exit code by one and exits non zero. The maximum is 99. sv exits 100 on error. If sv is called with a base name other than sv: it exits 1 on timeout or trouble sending the command; if the command is status, it exits 3 if the service is down, and 4 if the status is unknown; it exits 2 on wrong usage, and 151 on error. SEE ALSO
runsv(8), chpst(8), svlogd(8), runsvdir(8), runsvchdir(8), runit(8), runit-init(8) http://smarden.org/runit/ AUTHOR
Gerrit Pape <pape@smarden.org> sv(8)
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