Numeric vs String Comparison Operators

Numeric Comparison Operators

Bash's numeric comparison operators -- -eq, -ne, -gt, -ge, -lt, -le -- work inside [ ], [[ ]], and treat their operands strictly as integers. They correctly compare 9 and 10 as numbers, unlike string comparison would.

Example: Numeric Comparison Operators

#!/bin/bash
a=9
b=10
if [ "$a" -lt "$b" ]; then
    echo "$a is numerically less than $b"
fi

String Comparison Operators

String comparison uses =/== for equality and </> (inside [[ ]], or escaped as \</\> inside [ ]) for lexical (dictionary/byte) ordering, comparing character by character rather than numeric value. This means "9" > "10" is true as strings, since 9 sorts after 1.

Warning: This looks wrong numerically but is correct string behavior -- use -gt/-lt when you mean numeric comparison.

Example: String Comparison Operators

#!/bin/bash
a="9"
b="10"
if [[ $a > $b ]]; then
    echo "As strings, '$a' sorts after '$b'"
fi

Why Leading Zeros and Widths Matter for Strings

Because string comparison works character by character, values with different lengths or leading zeros can sort unexpectedly compared to their numeric meaning. Numeric comparison operators avoid this entirely by converting both sides to actual integers first.

Example: Why Leading Zeros and Widths Matter for Strings

#!/bin/bash
id1="007"
id2="10"
if [[ $id1 < $id2 ]]; then
    echo "As strings: '$id1' sorts before '$id2'"
fi
if [ "$id1" -lt "$id2" ]; then
    echo "As numbers: $id1 is less than $id2"
fi

Comparing Decimals with an External Tool

Bash's -eq/-lt/etc. and (( )) only support integers, so comparing decimal numbers like 3.5 requires an external tool such as bc or awk, since attempting [ 3.5 -gt 2 ] produces an 'integer expression expected' error. awk is commonly available and can perform the floating-point comparison directly.

Example: Comparing Decimals with an External Tool

#!/bin/bash
a="3.5"
b="2"
if awk -v x="$a" -v y="$b" 'BEGIN { exit !(x > y) }'; then
    echo "$a is greater than $b (decimal-aware comparison)"
fi