Programming Perl, 4th Edition

String Formats

Perl can create a string formatted by the usual printf conventions of the C library function sprintf. The sprintf version returns a string, and the printf version outputs either to the default or supplied filehandle:

sprintf FORMAT, LIST
printf FORMAT, LIST
printf FILEHANDLE FORMAT, LIST

The sprintf argument handling is a bit special. Its first argument is always taken as a scalar, even if it’s an array. This is probably not what you want since it uses @array in scalar context and only prints the number of elements in the array:

my @array = ( '%d %d %d', 1, 2, 3 );
sprintf @array;

The arguments for printf are different since it handles an optional FILEHANDLE argument.

The FORMAT string contains text with embedded field specifiers into which the elements of LIST are substituted, one per field. This feature is one of the things that Perl stole from C, so look at the sprintf(3) or printf(3) on your system for an explanation of the general principles.

Perl does its own sprintf formatting—it emulates the C function sprintf, but it doesn’t use it.^[229] As a result, any nonstandard extensions in your local sprintf(3) function are not available from Perl.

Perl’s sprintf permits the universally known conversions shown in Table 26-1.

Table 26-1. Formats for sprintf

Field	Meaning
%%	A literal percent sign
%b	An unsigned integer, in binary
%B	Like %b, but using an uppercase “B” with the # flag
%c	A character with the given ordinal value
%d	A signed integer, in decimal
%e	A floating-point number, in ...