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15.2 printf: Format and print data

printf does formatted printing of text. Synopsis:

 
printf format [argument]…

printf prints the format string, interpreting ‘%’ directives and ‘\’ escapes to format numeric and string arguments in a way that is mostly similar to the C ‘printf’ function. The differences are as follows:

A floating-point argument must use a period before any fractional digits, but is printed according to the LC_NUMERIC category of the current locale. For example, in a locale whose radix character is a comma, the command ‘printf %g 3.14’ outputs ‘3,14’ whereas the command ‘printf %g 3,14’ is an error.

printf interprets ‘\ooo’ in format as an octal number (if ooo is 1 to 3 octal digits) specifying a character to print, and ‘\xhh’ as a hexadecimal number (if hh is 1 to 2 hex digits) specifying a character to print.

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.

The processing of ‘\u’ and ‘\U’ requires a full-featured iconv facility. It is activated on systems with glibc 2.2 (or newer), or when libiconv is installed prior to this package. Otherwise ‘\u’ and ‘\U’ will print as-is.

The only options are a lone ‘--help’ or ‘--version’. See section Common options. Options must precede operands.

The Unicode character syntaxes are useful for writing strings in a locale independent way. For example, a string containing the Euro currency symbol

 
$ /usr/local/bin/printf '\u20AC 14.95'

will be output correctly in all locales supporting the Euro symbol (ISO-8859-15, UTF-8, and others). Similarly, a Chinese string

 
$ /usr/local/bin/printf '\u4e2d\u6587'

will be output correctly in all Chinese locales (GB2312, BIG5, UTF-8, etc).

Note that in these examples, the full name of printf has been given, to distinguish it from the GNU bash built-in function printf.

For larger strings, you don't need to look up the hexadecimal code values of each character one by one. ASCII characters mixed with \u escape sequences is also known as the JAVA source file encoding. You can use GNU recode 3.5c (or newer) to convert strings to this encoding. Here is how to convert a piece of text into a shell script which will output this text in a locale-independent way:

 
$ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \
    '\u4e2d\u6587\n' > sample.txt
$ recode BIG5..JAVA < sample.txt \
    | sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \
    > sample.sh

An exit status of zero indicates success, and a nonzero value indicates failure.


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