if文内で">"を使うと恐ろしいことが ref: http://qiita.com/toshi0383/items/b721b48fa780fe57e7c1

file0.txt

# 間違い！
#!/bin/bash
n1=${1:?}
n2=${2:?}
n3=${3:?}
if [ $n1 > $n2 ];then
    tmp=$n1
    n1=$n2
    n2=$tmp
fi
if [ $n2 > $n3 ];then
    tmp=$n2
    n2=$n3
    n3=$tmp
fi
if [ $n1 > $n2 ];then
    tmp=$n1
    n1=$n2
    n2=$tmp
fi
echo $n1 $n2 $n3

file1.txt

# 正しい
#!/bin/bash
n1=${1:?}
n2=${2:?}
n3=${3:?}
if [ $n1 -gt $n2 ];then
    tmp=$n1
    n1=$n2
    n2=$tmp
fi
if [ $n2 -gt $n3 ];then
    tmp=$n2
    n2=$n3
    n3=$tmp
fi
if [ $n1 -gt $n2 ];then
    tmp=$n1
    n1=$n2
    n2=$tmp
fi
echo $n1 $n2 $n3