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Full Discussion: Exec command - what is it doing here?
Top Forums Shell Programming and Scripting Exec command - what is it doing here? Post 302806377 by el_foz on Monday 13th of May 2013 03:27:13 AM
Old 05-13-2013
Code Exec command - what is it doing here?
Hi all,
Forgive me for asking for help with my first post, but I am struggling here. I've been asked to translate a bash script into a Windows script (probably batch or powershell, not sure yet), so the first step is obviously understand what the bash script is doing. But I have no experience in bash, very little in unix/linux, and no unix box to practice on.
I can't figure out the following code:

Code:
hmdir=/home/CBG_VCC_POD/NEVIS/PROD/
timestamp=to_cbg_`date +%y%m%d_%H%M%S`

exec 1>"$hmdir"log/to_cbg_log/${timestamp}.log 2>"$hmdir"log/to_cbg_log/${timestamp}.err

if [ ! -d "$hmdir"Inbound ]; then
	echo "Inbound directory not found!!!" >> "$hmdir"log/to_cbg_log/${timestamp}.err
	echo "Exits..." >> "$hmdir"log/to_cbg_log/${timestamp}.err
	cp "$hmdir"log/to_cbg_log/${timestamp}.err "$hmdir"to_cbg/${timestamp}.err
	exit 1
fi

...

The first two lines obviously setup variables. Following the exec line, the script continues with various if loops to create folders and copy and zip files. So what is the exec line doing?

From what I read, exec starts a new process, executes the passed parameter and then exits, but in this case there is no passed parameter as far as I can tell, and the script does continue after this line.

A colleague postulated that it is setting the output for the following lines in this script to go to the log file in case of a command returning "1" and to an err file in the case of a command returning "2", or something like that. Can anyone clarify?

Many thanks in advance.
Nick
 

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LEARN ABOUT REDHAT

newslog

NEWSLOG(5)							File Formats Manual							NEWSLOG(5)

NAME

       newslog - description of Usenet log files

DESCRIPTION

       Most  log  files  created by Usenet programs reside in the <pathlog in inn.conf> directory and have a ``.log'' extension.  Several versions
       are usually kept with an additional extension such as ``.1'', ``.2'', etc. -- the higher the number, the older the log.	The older versions
       are compressed.

       The scanlogs script and related utilities (see newslog(8)) are responsible for rotating and compressing these files.

       Some  log  files always have data, others only have data if there is a problem, and others are only created if a particular program is used
       or configuration parameter is set.  The innstat script (see newslog(8)) monitors the size of all log files.

       The following files will only accumulate data under the direction of control.ctl(5):
	      control.log miscctl.log newgroup.log rmgroup.log unwanted.log
       In order to create these files, the ``message'' and ``action'' fields of control.ctl should be chosen from the following table:
	      Message	  Action	 Meaning
	      all	  log=miscctl	 Log all messages by default
	      default	  log=miscctl	 Log unknown messages
	      newgroup	  doit=newgroup  Create group and log message
	      newgroup	  log=newgroup	 Log message
	      rmgroup	  doit=rmgroup	 Remove group and log message
	      rmgroup	  log=rmgroup	 Log message
	      ``other''   doit=miscctl	 log and process the message
	      ``other''   log=miscctl	 Log message
       Here, ``other'' refers to any other control message such as:
	      checkgroups ihave sendme sendsys senduuname version

       The following is a list of log files.

       control.log
	      This file maintains a count of the number of newgroup and rmgroup control messages seen for each newsgroup.  The	count  is  of  the
	      number  of  control messages with identical arguments, regardless if they were actually processed.  All control arguments, including
	      invalid ones, are counted.  This file is updated by tally.control, which is invoked by scanlogs if either the  newgroup  or  rmgroup
	      logs exist.  This file is not rotated.

       errlog This  file contains the standard output and standard error of any program spawned by innd(8).  The most common programs are the con-
	      trol-message handlers found in <pathcontrol in inn.conf>.  This file should be empty.  Scanlogs will print the  entire  contents	of
	      this log file if it is non-empty.

       expire.log
	      By  default,  when  news.daily  is  going  to expire old news articles, it writes the date to this file, followed by any output from
	      expire(8) and the ending date.  All lines but the first are indented four spaces.

       miscctl.log
	      When control.ctl is configured as described above, all control messages except newgroup and rmgroup are appended	to  this  file	by
	      writelog.   There  will be a summary line describing the message and the action taken, followed by the article indented by four spa-
	      ces, and a blank line.

       newgroup.log
	      When control.ctl is configured as described above, all newgroup messages are appended to this file using the same format as for mis-
	      cctl.log.

       news   This file logs articles received by innd.  Scanlogs summarizes the rejected articles reported in this file.

       news.crit
	      All  critical  error messages issued by innd are appended to this file via syslog(3).  This log file should be empty.  Scanlogs will
	      print the entire contents of this log file if it is non-empty.  You should have the following line in your syslog.conf(5) file.	(A
	      typical entry is shown; it should agree with <pathlog in inn.conf>)
		     news.crit	<pathlog in inn.conf>/news.crit

       news.err
	      All  major  error  messages  issued  by innd are appended to this file via syslog(3).  This log file should be empty.  Scanlogs will
	      print the entire contents of this log file if it is non-empty.  You should have the following line in your syslog.conf(5)  file:	(A
	      typical entry is shown; it should agree with <pathlog in inn.conf>)
		     news.err  <pathlog in inn.conf>/news.err

       news.notice
	      All  standard  error messages and status messages issued by innd are appended to this file via syslog(3).  Scanlogs uses the perl(1)
	      script innreport(8) to summarize this file.  You should have the following line in your syslog.conf(5) file:  (A	typical  entry	is
	      shown; it should agree with <pathlog in inn.conf>)
		     news.notice  <pathlog in inn.conf>/news.notice

       nntpsend.log
	      The nntpsend(8) programs appends all status messages to this file.

       rmgroup.log
	      When control.ctl is configured as described above, all rmgroup messages are appended to this file using the same format as for misc-
	      ctl.log.

       unwanted.log
	      This log maintains a count of the number of articles that were rejected because they were posted to newsgroups that do not exist	at
	      the  local  site.   This	file is updated by tally.unwanted and maintained in reverse numeric order (the most popular rejected group
	      first).  This file is not rotated.

HISTORY

       Written by Landon Curt Noll <chongo@toad.com> and Rich $alz  <rsalz@uunet.uu.net>  for  InterNetNews.   This  is  revision  1.6.6.1,  dated
       2000/08/17.

SEE ALSO

       control.ctl(5), ctlinnd(8), expire(8), inn.conf(5), innd(8), news.daily(8), nntpsend(8), newslog(8).

																	NEWSLOG(5)
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