How to find min of two variables in linux - linux

Question

i have two variables
$a and $b
is there shell script command to assign the value of minimum variable to $c
i.e
$c = min($a,$b)
and some command that can work across all platforms hp-ux,aix,linux_x_64
thanks in advance
EDIT:
default shell is ksh
and below the script im trying to run
rm abc.log
near_dr=`sqlplus -s tcs384160/tcs#1234 <<\EOF
set pagesize 0 feedback off verify off heading off echo off
select max(sequence#) from v$archived_log where applied='YES' and thread#=1 and
dest_id=2;
exit;
EOF`
DR=`sqlplus -s tcs384160/tcs#1234 <<\EOF
set pagesize 0 feedback off verify off heading off echo off
select max(sequence#) from v$archived_log where applied='YES' and thread#=1 and
dest_id=3;
exit;
EOF`
safe_var=$([ $near_dr -le $DR ] && echo "$near_dr" || echo "$DR")
echo $safe_var;
ulimit=`expr $safe_var - 30`;
llimit=`expr $ulimit - 1000`;
echo $llimit;
echo $ulimit;
i=$llimit
while [ $i -le $ulimit ];
do
ls evdprd_1_${i}_*.arc>>abc.log;
let i=i+1;
done;
recover -s ttlhydnwr -c tphtpsd2<<EOF >> abc.log
ls -1 *.arc
exit
EOF
sed -e 's/[\t ]//g;/^$/d' abc.log > abc1.log
awk '++seen[$0] == 2' abc1.log > actual.log
please ignore the sqlplus parts as those are working fine the only problem is the $safe_var needing the minimum of the two values

Answer 1

There is no function, but you can create it:
(( $a <= $b )) && echo "$a" || echo "$b"
The condition && action1 || action2 does evaluate the condition. If it is true, then perform action1; otherwise, perform action2.
To store the result into a variable, do:
min=$( (( $a <= $b )) && echo "$a" || echo "$b" )
Update
It seems that the $( (( )) ) syntax is giving problems. Hence, let's replace it to:
[ $a -le $b ] && echo "$a" || echo "$b"
or assigning value:
min=$([ $a -le $b ] && echo "$a" || echo "$b")
Sample
$ a=3
$ b=4
$ [ $a -le $b ] && echo "$a" || echo "$b"
3
$ b=1
$ [ $a -le $b ] && echo "$a" || echo "$b"
1
$ b=3
$ [ $a -le $b ] && echo "$a" || echo "$b"
3

Answer 2

You could do in this way too:
x=1
y=2
echo $(($x<$y?$x:$y))
1
To store value in other variable:
z=$(($x<$y?$x:$y)) #Min
z=$(($x<=$y?$x:$y)) #Min and equal
z=$(($x>$y?$x:$y)) #Greater
z=$(($x>=$y?$x:$y)) #Greater and equal

Answer 3

In ksh, this works fine
$ near_dr=5 DR=10
$ save_var=$(( near_dr < DR ? near_dr : DR )) ; echo $save_var
5
$ near_dr=15 DR=10
$ save_var=$(( near_dr < DR ? near_dr : DR )) ; echo $save_var
10
$ near_dr=15 DR=15
$ save_var=$(( near_dr < DR ? near_dr : DR )) ; echo $save_var
15
So you can write a function:
min() {
echo $(( $1 < $2 ? $1 : $2 ))
}
safe_var=$(min $near_dr $DR)
This is the same as #Liaraz's answer, except "Variables can be referenced by name within an arithmetic
expression without using the parameter expansion syntax." (ksh man page, section Arithmetic evaluation)

Answer 4

Ksh93 custom arithmetic function example:
function .sh.math.min a b {
.sh.value=$(( a<b ? a : b ))
}
$ echo $(( min(1,3) ))
1
$ echo $(( min(5,3) ))
3

Answer 5

if you are sure the value of variables are integers, use #fedorqui's answer. It's short and neat.
however, if you are not sure about that, they could be e.g. float numbers:
kent$ a=3.57
kent$ b=13.5
kent$ (($a < $b)) && echo "y" || echo "n"
bash: ((: 3.57 < 13.5: syntax error: invalid arithmetic operator (error token is ".57 < 13.5")
n
this would work for all cases:
kent$ awk -v a="$a" -v b="$b" 'BEGIN{print (a>b)?b:a}'
3.57