05-08-2015
Changing any program while it is running (C, C++, FORTRAN, ... a.out), awk script, or shell script) might have absolutely no effect (the program was loaded when it started and runs from memory independent of the contents of the file(s) it was loaded from), or might cause it to die a horrible death when a block of memory containing commands being processed changes into something else that might be a mix of characters that don't quite make up the new program or the old program. Specifying when something will continue working unchanged may vary depending on the OS, the shell, the filesystem type from which the program is loaded, whether it is a statically linked binary, a dynamically linked binary, or an interpreted language, whether or not the sticky bits that way), and lots of other conditions.
If you have a separate script that you invoke when you want to produce output after lengthy computational loops in a script, and you change that separate script while the base script is performing one of those lengthy computations; you might get what you want. If you try to change the text of a function that has already been loaded by the shell, later invocations of that function aren't likely to be affected by changes to the source for that function. But if modifying that function at the start of your shell script changes the length of the script and your script consumes more than one block on disk, your script could die when it loads the next block of the script and finds that the command that crossed the boundary between two disk blocks duplicated or dropped a few characters, all bets are off.
Although you might be able to figure out what will happen to you on a particular version of an OS and shell combination, there is no guarantee that the same thing will happen after you upgrade to the next update of that OS or shell.
10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
1 #!/bin/ksh
2 ################################################################
3 # Written by Johnson 12/03/2008
4 # Version 1.0
5 # This script executes some SQL to provide Spike Check Report to TNS team.
6 ... (3 Replies)
Discussion started by: shivanete
3 Replies
2. Shell Programming and Scripting
Hi
I have a question
Suppose i have three scripts & i have created a top level script to run these.
eg.
leaf1.csh
leaf2.csh
leaf3.csh
top.csh
Now in top.csh i have written
#!/bin/csh
leaf1.csh
leaf2.csh
leaf3.csh
Now my question is when i run this top level script when it... (1 Reply)
Discussion started by: sarbjit
1 Replies
3. Shell Programming and Scripting
Hi,
I have a requirement as below which needs to be done viz UNIX shell script
(1) I have to connect to an Oracle database
(2) Exexute "SELECT field_status from table 1" query on one of the tables.
(3) Based on the result that I get from point (2), I have to update another table in the... (6 Replies)
Discussion started by: balaeswari
6 Replies
4. AIX
Hi,
I'm trying to run database restore script with the nohup command as it will run for long hours since if I run it normally, the putty session will become inactive and the restore gets terminated. The command I use is
nohup db2 -tvf FBR_NODE0000.scr -z FBR_NODE0000.log &
But the problem is... (2 Replies)
Discussion started by: vkcool.17
2 Replies
5. Shell Programming and Scripting
is_number()
{
echo $1|egrep '^*$' 2>&1 1>/dev/null
return $?
}why the following snippet always give an output as "no" and never "yes" whatever the parameter I give to function is_number?
if ]; then echo yes; else echo no; fi
In addition, the function is_number() is... (5 Replies)
Discussion started by: biglau
5 Replies
6. Shell Programming and Scripting
Hi All,
After reading that the sort command in Linux can be made to use many processor cores just by using a simple script which I found on the internet, I was wondering if I can use similar techniques for programs like the awk and sed?
#!/bin/bash
# Usage: psort filename <chunksize>... (7 Replies)
Discussion started by: shoaibjameel123
7 Replies
7. Shell Programming and Scripting
Hello!
I'm trying to run this code to print the body of an html document (all text in between <body> and </body>) from a script but am unsure how to call it from the command line interface.
/<body>/,/<\/body>/
1s/.*<body>//
$s/<\/body>.*//p
I have tried to call it using this:
sed... (6 Replies)
Discussion started by: bgnersoon2be#1
6 Replies
8. Shell Programming and Scripting
Hi I was trying to fetch data from database. But the number of rows exported were huge so i got the error. Experts please advice. Thanks a lot for your supprt. #: ./script.sh ./script.sh: xmalloc: subst.c:3076: cannot allocate 1401346369 bytes (0 bytes allocated) (2 Replies)
Discussion started by: brij123
2 Replies
9. UNIX for Dummies Questions & Answers
Hi
I searched this forum before posting the question, but couldnt find it, the issue
i'm facing is, i'm trying to select a column from a netezza table from a korn
shell script, but the query runs
var=$(nzodbcsql -q "select MAX(millcount) from table1";)
echo $var
it returns the value like... (10 Replies)
Discussion started by: maximus_jack
10 Replies
10. Shell Programming and Scripting
so i have a script that takes a while to complete and its cpu intensive. this script is being used by several users. i want to make sure only 1 user can run this script at any given time.
i originally thought of running a while loop to egrep the process table of the PID ($$) of the process,... (7 Replies)
Discussion started by: SkySmart
7 Replies
LEARN ABOUT OSF1
uudemon.cleanu
uudemon(4) Kernel Interfaces Manual uudemon(4)
NAME
uudemon.admin, uudemon.cleanu, uudemon.hour, uudemon.poll - Administrative shell scripts for polling remote systems, cleaning up spool
directories, reporting status to the system administrator, and routine invocations of the uuxqt and uusched daemons
SYNOPSIS
These shell scripts reside in the following directory:
/usr/lib/uucp
DESCRIPTION
All the scripts can be run from the command line or can be run automatically by the cron daemon. To automatically run the scripts, remove
the comment character (#) from the beginning of the relevant line in the /var/spool/cron/crontabs/uucp file.
This script reports status to the system administrator. It issues the uustat command to find out the status of uucp jobs. It mails the
results to the uucp login ID. The script may be modified to send mail to any login ID such as the uucp administrative login ID (uucpa) or
root. This script cleans up the /var/spool/uucp and /var/spool/uucppublic directories by running the uucleanup command. The uucleanup com-
mand is run with the following parameters: -C7, -D7, X2, -o2, -W1. This script runs the uusched and uuxqt daemons in the background. This
script polls the systems listed in the /usr/lib/uucp/Poll file. The uudemon.poll script should be scheduled before the uudemon.hour
script. This allows uudemon.poll to create any command files before cron runs the uudemon.hour script.
FILES
Contains the uudemon.admin, uudemon.cleanu, uudemon.hour and uudemon.poll files. Contains the uucp file.
RELATED INFORMATION
Commands: cron(8), uucleanup(8), uusched(8), uuxqt(1)
Files: /usr/lib/uucp delim off
uudemon(4)