Bash – Using Dashes in Printf

It is as expected, it is "round to even", or "Banker's rounding".

A related site answer explain it.

The issue that such rule is trying to solve is that (for numbers with one decimal),

• x.1 up to x.4 are rounded down.
• x.6 up to x.9 are rounded up.

That's 4 down and 4 up.
To keep the rounding in balance, we need to round the x.5

• up one time and down the next.

That is done by the rule: « Round to nearest 'even number' ».

In code:

sh LC_NUMERIC=C printf '%.0f ' "$value"
awk echo "$value" | awk 'printf( "%s", $1)'

Options:

In total, there are four possible ways to round a number:

1. The already explained Banker's rule.
2. Round towards +infinite. Round up (for positive numbers)
3. Round towards -infinite. Round down (for positive numbers)
4. Round towards zero. Remove the decimals (either positive or negative).

Up

If you do need "round up (toward +infinite)", then you can use awk:

value=195.5

awk echo "$value" | awk '{ printf("%d", $1 + 0.5) }'
bc echo "scale=0; ($value+0.5)/1" | bc

Down

If you do need "round down (Toward -infinite)", then you can use:

value=195.5

awk echo "$value" | awk '{ printf("%d", $1 - 0.5) }'
bc echo "scale=0; ($value-0.5)/1" | bc

Trim decimals.

To remove the decimals (anything after the dot).
We could also directly use the shell (works on most shells - is POSIX):

value="127.54"    ### Works also for negative numbers.

shell echo "${value%%.*}"
awk echo "$value"| awk '{printf ("%d",$0)}'
bc echo "scale=0; ($value)/1" | bc

To avoid the double-expansion problem (\u is processed before %s), you can use %b, at least in Bash printf:

printf '%b\n' \\u0024 \\u0025

You can pre-process your input in various ways:

set 0024 0025
printf '%b\n' "${@/#/\\u}"

The standalone printf, as implemented in GNU coreutils, has the following restrictions on Unicode character specifications:

printf interprets two character syntaxes introduced in ISO C 99: ‘\u’ for 16-bit Unicode (ISO/IEC 10646) characters, specified as four hexadecimal digits hhhh, and ‘\U’ for 32-bit Unicode characters, specified as eight hexadecimal digits hhhhhhhh. printf outputs the Unicode characters according to the LC_CTYPE locale. Unicode characters in the ranges U+0000…U+009F, U+D800…U+DFFF cannot be specified by this syntax, except for U+0024 ($), U+0040 (@), and U+0060 (`).

This explains why you can’t produce % in this manner.