Hex to Decimal in AWK

Staring at a column of values like 1F90 and need plain numbers? This guide shows you hex to decimal in awk with a few lines of scripting, so your hexadecimal values become decimal numbers right inside the pipeline. You get the short gawk one-liner, a portable fallback for Unix-based environments, and the checks that keep your log files and network data accurate.

How to Convert Hex to Decimal in AWK with strtonum and printf

The quickest route is a single built-in function. GNU AWK ships strtonum(), which reads a string such as 0x7B2C and returns a number, and you hand that number to printf or print. The pipeline below reads one hex string per line and prints its decimal form. Use the base36 to hex converter when a short-URL ID or generated token encoded in Base36 needs to be converted back to hex.

echo "7B2C" | awk '{ printf "%d\n", strtonum("0x" $1) }'
# Output: 31532

Here "0x" $1 glues the prefix onto the field, strtonum parses the result as base-16, and %d prints the integer. You can drop printf and use plain print strtonum("0x" $1) when you do not need padding or a custom layout.

Method 1: Use gawk strtonum with a format specifier

Whenever a script has to keep columns aligned, the format specifier does the work. %d gives a bare integer, %8d right-aligns it in eight characters, and %08d pads with zeros. Running gawk explicitly makes it obvious which interpreter your script depends on:

printf 'web01 1F90\ndb02 0CEA\n' | gawk '{ printf "%-6s %6d\n", $1, strtonum("0x" $2) }'
# web01   8080
# db02    3306

Each hex port in the second column becomes a decimal port while the first column passes through untouched.

Method 2: Manual conversion with a hex2dec function for older AWK versions

Some systems ship an older AWK that has no strtonum; the stock FreeBSD awk and mawk are common examples, and calling the missing function ends with an "undefined function" error. For those cases a manual conversion built on substr, index and toupper is fully portable:

function hex2dec(h,    i, c, d, n) {
  h = toupper(h)
  sub(/^0X/, "", h)
  n = 0
  for (i = 1; i <= length(h); i++) {
    c = substr(h, i, 1)
    d = index("0123456789ABCDEF", c) - 1
    if (d < 0) return -1
    n = n * 16 + d
  }
  return n
}
{ print $1, hex2dec($2) }

The loop walks the hex digits from left to right. For every character, index() finds its position in the digit list, which is its value, and the running total is multiplied by 16 before the next digit is added. A return value of -1 flags a character that is not valid.

Hex to Decimal Conversion in AWK for Log Files and Hex IDs

Real input is rarely a clean column. Hex values hide inside system logs, memory dumps and binary protocols dumps, mixed with text, and inline data processing lets you convert them without any external helper.

Parsing hex fields from log files

Suppose a web server writes lines such as 10.20.30.40 GET /status 200 size=0x3F7A91 req=0x9E4. A short loop finds every hex field, splits off its name, and prints the decimal result:

awk '{ for (i = 1; i <= NF; i++)
  if ($i ~ /^(size|req)=0x[0-9A-Fa-f]+$/) {
    split($i, kv, "=")
    printf "%s=%d\n", kv[1], strtonum(kv[2])
  } }' access.log
# size=4160145
# req=2532

The same pattern works for hex IDs and a hex timestamp field, and it keeps the original text intact when you print the other columns next to the converted ones.

Hex strings with or without the 0x prefix

The 0x prefix matters. strtonum("0x9E4") parses base-16, while strtonum("9E4") reads the string as a decimal number and stops at the first letter. That is why raw hex input always needs the prefix glued on first. Uppercase and lowercase letters both work, so 0x9e4 and 0x9E4 give the same answer; the manual function above handles case itself with toupper.

Common Hexadecimal Conversion Pitfalls in AWK Scripts

A conversion that runs is not always a conversion that is right. Three traps cause almost every bad result you will meet when you convert hex values in a pipeline.

The concatenation trap: 0x$7 is not "0x" $7

In awk the unquoted 0x is a number followed by a variable named x, and the missing operator means concatenation of two empty-or-zero values with the field. The unset variable x is auto set to 0 the first time awk sees it, so the text left behind starts with digits, and strtonum keeps only the leading digits and silently ignores everything from the first letter on. A field holding 08BA collapses to 8, even though the hexadecimal value really equals 2234, so the printed numbers look plausible but never match a hand check. Quote the prefix as a string, as in "0x" $7, and you get the full value.

Leading zeros and edge cases

Leading zeros are harmless for the number but matter for display. 00FF converts to 255 in both methods, and if the width must survive you need a %05d style format. Test edge cases before you trust a script, and know what each method does with them: strtonum("0x") on an empty field returns 0, strtonum("0xG1") stops at the G and also returns 0, while the manual hex2dec returns -1 for the same bad character. Very large values are stored as floating-point numbers, so anything past 2⁵³ loses precision in awk, and a 16-digit hex field needs a different tool.

Version and portability checks

Run awk --version first. If it reports GNU Awk, strtonum exists; if not, either install gawk or ship the hex2dec function with your script. Installing a second interpreter beside the system one avoids breaking older scripts that rely on the stock awk.

Hex to Decimal Converter Alternatives: bc, Perl, Python and More

Awk is not the only way to convert hex to decimal, and the right pick depends on how much of your pipeline is already built.

Python, JavaScript and C++ equivalents

When the conversion moves out of the shell and into a program, every language has a built-in function. Python uses int("7B2C", 16), JavaScript uses parseInt("7B2C", 16), and C++ uses std::stoi("7B2C", nullptr, 16); all three return 31532. For one-off checks, a hex to decimal converter in your browser gives the same answer, and for the opposite direction look at decimal to hex tools or printf "%X".