Sponsored Content
Top Forums Shell Programming and Scripting Usage of '-' in eval command. Post 302878493 by rbatte1 on Friday 6th of December 2013 10:40:03 AM
Old 12-06-2013
The hyphen can be used in CoBOL code, but it is considered as plain text for Unix shells. I've fallen across this the other way around when I wanted to set a variable to a value built from another variable like this:-
Code:
fileheader=myfile
rundate=`date +%Y%m%d`
filename=$fileheader_$rundate

I wanted to end up with myfile_20131206 as the filename format and I got very confused because it always evaluated to just 20131206 (or whatever the date was)

This was because the underscore is considered part of the variable name and the variable fileheader_ was undefined. This is not pretty, but I had to change the code to read:-
Code:
fileheader=myfile
rundate=`date +%Y%m%d`
filename=${fileheader}_$rundate

.... and learn from my error.

I too would like to know what you are actually trying to achieve. We might have a better way to do it, save you some hassle and provide something for others to read and learn from. Indeed, I'm quite happy to learn myself if there is a better way than I am currently using.



Robin
This User Gave Thanks to rbatte1 For This Post:
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Access to database/eval command

Hi i have the following code: if(($line!=1) and (@field!='\$')){ print ( "\nTRY TO CONNECT TO DATABASE................\n"); my $dbh = DBI->connect($dsn, $user, $pass); print ("CONNECTED TO DATABASE\n"); eval ... (1 Reply)
Discussion started by: chriss_58
1 Replies

2. HP-UX

how can I find cpu usage memory usage swap usage and logical volume usage

how can I find cpu usage memory usage swap usage and I want to know CPU usage above X% and contiue Y times and memory usage above X % and contiue Y times my final destination is monitor process logical volume usage above X % and number of Logical voluage above can I not to... (3 Replies)
Discussion started by: alert0919
3 Replies

3. Shell Programming and Scripting

Help with eval usage for string containing Environment Variable

Help !! First, Thanks in Advance Here is what I have I have an environment Variable, let's call it v_VALUE. v_VALUE="\$ORACLE_HOME/bin" Hence, the location is ORACLE_HOME is not evaluated. ORACLE_HOME happens to be /app/oracle/product/10.1.2 I need a method of returning the... (1 Reply)
Discussion started by: dhangliter
1 Replies

4. Shell Programming and Scripting

assignment to variable from eval command

Hi Gurus, I am having 2 parameters as below parm1=value1 parm2=parm1 I want to evaluate parm1 value using eval echo \$$parm2 and later i want to assign this value to other variable which i will be using in if statement like : if ]; then do this....... fi could you please suggest... (5 Replies)
Discussion started by: k_vikash
5 Replies

5. UNIX for Dummies Questions & Answers

Command to display the space usage (memory usage) of a specific directory.

Hi all, Can you please tell me the command, with which one can know the amount of space a specific directory has used. df -k . ---> Displays, the amount of space allocated, and used for a directory. du -k <dir name> - gives me the memory used of all the files inside <dir> But i... (2 Replies)
Discussion started by: abhisheksunkari
2 Replies

6. Shell Programming and Scripting

Eval command help

I have file called myfile which has the text "myserver" in it. I need to have a command to ping "myserver". How would I do that? I tried when I type at the terminal I get the output as . How do I do something like a ? thanks, Nick (5 Replies)
Discussion started by: nikhilfake
5 Replies

7. Shell Programming and Scripting

Strange result of eval, how does eval really work with ssh?

Hi all, some small script with eval turned me to crazy. my OS is linux Linux s10-1310 2.6.16.53-0.8.PTF.434477.3.TDC.0-smp #1 SMP Fri Aug 31 06:07:27 PDT 2007 x86_64 x86_64 x86_64 GNU/Linux below script works well #!/bin/bash eval ssh remotehost date eval ssh remotehost ls below... (1 Reply)
Discussion started by: summer_cherry
1 Replies

8. Shell Programming and Scripting

Help with perl eval command .....

Hi All, I read the above written code (perl code) in another perl script and evaluates this code for each line of text file,but using exit statement in code make this not to work and i could not get the desired results. However if i use return it works fine. I just need to know why it doesn't... (1 Reply)
Discussion started by: sarbjit
1 Replies

9. Shell Programming and Scripting

Error in eval eval command to print html tags

anyone has any info on why this is complaining??? vivek@vivek-c5e55ef2e ~/TAC $ zoneCounter=1 vivek@vivek-c5e55ef2e ~/TAC $ optUsage1=23% vivek@vivek-c5e55ef2e ~/TAC $ eval eval echo "<th>Zone $zoneCounter </th><th align=\"left\"> \$optUsage$zoneCounter </th>" -bash: syntax error... (1 Reply)
Discussion started by: vivek d r
1 Replies

10. Shell Programming and Scripting

Error in eval eval command to print html tags

anyone has any info on why this is complaining??? vivek@vivek-c5e55ef2e ~/TAC $ zoneCounter=1 vivek@vivek-c5e55ef2e ~/TAC $ optUsage1=23% vivek@vivek-c5e55ef2e ~/TAC $ eval eval echo "<th>Zone $zoneCounter </th><th align=\"left\"> \$optUsage$zoneCounter </th>" -bash: syntax error... (13 Replies)
Discussion started by: vivek d r
13 Replies
eval(1T)						       Tcl Built-In Commands							  eval(1T)

__________________________________________________________________________________________________________________________________________________

NAME
eval - Evaluate a Tcl script SYNOPSIS
eval arg ?arg ...? _________________________________________________________________ DESCRIPTION
Eval takes one or more arguments, which together comprise a Tcl script containing one or more commands. Eval concatenates all its argu- ments in the same fashion as the concat command, passes the concatenated string to the Tcl interpreter recursively, and returns the result of that evaluation (or any error generated by it). Note that the list command quotes sequences of words in such a way that they are not further expanded by the eval command. EXAMPLE
This procedure acts in a way that is analogous to the lappend command, except it inserts the argument values at the start of the list in the variable: proc lprepend {varName args} { upvar 1 $varName var # Ensure that the variable exists and contains a list lappend var # Now we insert all the arguments in one go set var [eval [list linsert $var 0] $args] } KEYWORDS
concatenate, evaluate, script SEE ALSO
catch(1T), concat(1T), error(1T), list(1T), subst(1T), tclvars(1T) ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +--------------------+-----------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +--------------------+-----------------+ |Availability | SUNWTcl | +--------------------+-----------------+ |Interface Stability | Uncommitted | +--------------------+-----------------+ NOTES
Source for Tcl is available on http://opensolaris.org. Tcl eval(1T)
All times are GMT -4. The time now is 08:36 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy