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if then else; no variable match but statement executes anyway.

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# 1  
Old 09-27-2012
if then else; no variable match but statement executes anyway.
My first then statement is executing even though there is no match between the variables. each subsequent if then statement is also executing.

Why do they execute when there is no match in the dates?



Code:
yr=`date +%y`
date1=12-31-$yr
date=`date +%m-%d-%y`



set -vx
if  [ "$date" == "$date1" ] ;
        then
                #rm /root/sar_data/hist_sar*-*-2012.tar.gz
                printf "2012\n"
fi
        if [ "$date"=="$date1" ]
                then
                rm /root/sar_data/hist_sar*-*-2013.tar.gz
                printf "2013\n"
fi
        if  [ $date==$date1 ]
                then
                rm /root/sar_data/hist_sar*-*-2014.tar.gz
                printf "2014\n"
fi
if  [ $date=$date1 ]
                then
                rm /root/sar_data/hist_sar*-*-2015.tar.gz
                printf "2015\n"
fi

Last edited by Scrutinizer; 09-27-2012 at 09:57 PM.. Reason: code tags
# 2  
Old 09-27-2012
Quote:
Originally Posted by bash_in_my_head
My first then statement is executing even though there is no match between the variables. each subsequent if then statement is also executing.

Why do they execute when there is no match in the dates?



yr=`date +%y`
date1=12-31-$yr
date=`date +%m-%d-%y`



set -vx
if [ "$date" == "$date1" ] ;
then
#rm /root/sar_data/hist_sar*-*-2012.tar.gz
printf "2012\n"
fi
if [ "$date"=="$date1" ]
then
rm /root/sar_data/hist_sar*-*-2013.tar.gz
printf "2013\n"
fi
if [ $date==$date1 ]
then
rm /root/sar_data/hist_sar*-*-2014.tar.gz
printf "2014\n"
fi
if [ $date=$date1 ]
then
rm /root/sar_data/hist_sar*-*-2015.tar.gz
printf "2015\n"
fi
The arguments to test need to be separate operands. Your first test:
Code:
if  [ "$date" == "$date1" ] ;

is working as you expect because there are spaces surrounding the "==". The rest all evaluate to true because without the spaces around "==" and "=", you just have one operand to test and it evaluates to true because it is not an empty string.
# 3  
Old 09-28-2012
I am trying to match a date when the date on the right side which will be 12-21-year. I want a match. the date on the left will

so I want 12-30-12 = 12-30-12 to match and when they do I would like to have the command in the statement execute. If there is not a data match I would like nothing to happen.

What is the best way to accomplish this in my example.

Thanks
# 4  
Old 09-28-2012
The first if command in your example does exactly what you want when I try it. (I use ksh; you haven't said what shell you're using.) In other words, it does not print 2012 because "12-31-12" is not "09-28-12".) It should work with any shell that supports the basic tenets of the shell command language defined by the the original Bourne shell. (This includes at least bash, ksh, and sh.)

The test statements in the rest of your if commands all evaluate to true because the strings "09-28-12==12-31-12" and "09-28-12=12-31-12" are not empty strings. In these cases == and = are just parts of a string; they are not comparison operators.

Assuming you are using bash, ksh, sh or a similar shell (NOT csh nor tcsh), you should get what you seem to want if you change: "$date"=="$date1" to "$date" == "$date1", $date==$date1 to $date == $date1, and $date=$date1 to $date = $date1, respectively.

You may note that the standards specify = as the operator to compare strings for equality, but I don't know of any POSIX-conforming shell that doesn't also recognize == (and most shell maintainers prefer == and consider = obsolete).
# 5  
Old 09-29-2012
Code:
# test command need 3 arguments when like to compare strings
# value1 operator value2
# operator:  !=  or  = 
# => need spaces between args
if [  "$date" = "$date1" ] ; then
    echo same
fi

# or
[ "$date" = "$date1" ]  && echo same
# or
[[ "$date" == "$date1" ]]  && echo same

[
and
[[
are not same.
[[ is newer and include more functionality as old test command (sortly [ )
Last edited by kshji; 09-29-2012 at 10:58 AM..
# 6  
Old 10-02-2012
Code:
#!/bin/bash
Now I would like to iterate through two arrays.
array3=(12 13 14 15 16 17 18 19 20 21 22 23 24 25)
array4=(13 14 15 16 17 18 19 20 21 22 23 24 25)

for i in ${array3[@]}  && for q in ${array4[@]};
do
[ "$date" = "12-31-"$q"" ] && rm /root/sar_data/hist_sar*-*-20"$i".tar.gz ; printf "20"$i"\n"
done

ERROR:
for i in ${array3[@]} && for q in ${array4[@]};
./sarbackup.sh: line 73: syntax error near unexpected token `&&'
./sarbackup.sh: line 73: `for i in ${array3[@]} && for q in ${array4[@]};'

I did not think this would work but I tried in anyway for fun. This does however work to display what I am trying to accomplish.

Please show me a way that works with proper syntax.

thanks
# 7  
Old 10-03-2012
for need do and done.
Code:
# this format works
for ...
do
     for ....
     do
     done
done

"$date" = "12-31-"$q""
=> no need to join strings and variable values, in the shells in the double quoting variable values has taken. Between " " almost every special characters lost the special meaning except \ and $.
"$date" = "12-31-$q"
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