01-03-2006
how to get variable to re-evaluate itself?
Probably a simple one.
Basically I am retrieving a number from a file - setting a variable against it and then incrementing this by 1 and using this as an entry number in a log file for messages. I need the variable to re-evalute itself each time I call it so I get the latest number in the file - how do I do this? my script is basically as follows:
The number within test4.csv is updated every 2 seconds ... so the second time I echo $e I hope to see the latest number incremented by one
#!/usr/bin/ksh
d=`tail -1 test4.csv | cut -f1 -d" "`
e=$((d + 1))
echo e is $e
sleep 3
echo e is $e
sleep 3
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LEARN ABOUT OPENSOLARIS
echo
echo(1B) SunOS/BSD Compatibility Package Commands echo(1B)
NAME
echo - echo arguments to standard output
SYNOPSIS
/usr/ucb/echo [-n] [argument]
DESCRIPTION
echo writes its arguments, separated by BLANKs and terminated by a NEWLINE, to the standard output.
echo is useful for producing diagnostics in command files and for sending known data into a pipe, and for displaying the contents of envi-
ronment variables.
For example, you can use echo to determine how many subdirectories below the root directory (/) is your current directory, as follows:
o echo your current-working-directory's full pathname
o pipe the output through tr to translate the path's embedded slash-characters into space-characters
o pipe that output through wc -w for a count of the names in your path.
example% /usr/bin/echo "echo $PWD | tr '/' ' ' | wc -w"
See tr(1) and wc(1) for their functionality.
The shells csh(1), ksh(1), and sh(1), each have an echo built-in command, which, by default, will have precedence, and will be invoked if
the user calls echo without a full pathname. /usr/ucb/echo and csh's echo() have an -n option, but do not understand back-slashed escape
characters. sh's echo(), ksh's echo(), and /usr/bin/echo, on the other hand, understand the black-slashed escape characters, and ksh's
echo() also understands a as the audible bell character; however, these commands do not have an -n option.
OPTIONS
-n Do not add the NEWLINE to the output.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWscpu |
+-----------------------------+-----------------------------+
SEE ALSO
csh(1), echo(1), ksh(1), sh(1), tr(1), wc(1), attributes(5)
NOTES
The -n option is a transition aid for BSD applications, and may not be supported in future releases.
SunOS 5.11 3 Aug 1994 echo(1B)