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Perl sprintf Function
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The Perl sprintf function returns a string formatted by the usual printf conventions of the C library function sprintf. Instead of the printf function which prints the string to the current output filehandle or to the one specified by a filehandle, the sprintf function will return the formatted string in a scalar variable.In this short free tutorial I'll show you a few examples about how to use this function to get a specific formatted string. The syntax form of the Perl sprintf function is as follows: $string = sprintf FORMAT, LIST
where the FORMAT is used to return a formatted string based on the LIST values.The sprintf function FORMAT allows you to use the following conversions:
| Symbol | Meaning, Example | | %% | a percent sign | | %c | a character with the given number
my $string = sprintf '%c', 0x61;
print "$string\n"; # it displays: a
| | %s | a string
my $string = sprintf '%s', "abcd";
print "$string\n"; # it displays: abcd
| | %d | a signed integer, in decimal
my $string = sprintf '%d', 123415;
print "$string\n"; # it displays: 123415
| | %D | a synonym for %ld
my $string = sprintf '%ld', 234151345;
print "$string\n"; # it displays: 234151345
| | %i | a synonym for %d
my $string = sprintf '%i', -17324;
print "$string\n"; # it displays: -17324
| | %u | an unsigned integer, in decimal
my $string = sprintf '%u', 2217324;
print "$string\n"; # it displays: 2217324
| | %U | a synonym for %lu
my $string = sprintf '%U', 2217324334;
print "$string\n"; # it displays: 2217324334
| | %o | an unsigned integer, in octal
my $string = sprintf '%o', 934522;
print "$string\n"; # it displays: 3441172
| | %O | a synonym for %lo | | %x | an unsigned integer, in hexadecimal
my $string = sprintf '%x', 934522;
print "$string\n"; # it displays: e427a
| | %X | like %x, but using uppercase letters
my $string = sprintf '%X', 934522;
print "$string\n"; # it displays: E427A
| | %e | a floating-point number in scientific notation
my $string = sprintf '%e', -12.345;
print "$string\n"; # it displays: -1.234500e+001
| | %E | like %e, but using uppercase "E"
my $string = sprintf '%E', -12.345;
print "$string\n"; # it displays: -1.234500E+001
| | %f | a floating-point number in fixed decimal notation
my $string = sprintf '%f', -12.345;
print "$string\n"; # it displays: -12.345000
| | %F | a synonym for %f
my $string = sprintf '%F', -12.345;
print "$string\n"; # it displays: -12.345000
| | %g | a floating-point number in %e or %f notation
my $string = sprintf '%g', -1.234500E+1;
print "$string\n"; # it displays: -12.345
| | %G | like %g, but with an uppercase "E", if applicable | | %b | an unsigned integer, in binary
my $string = sprintf '%b', 123;
print "$string\n"; # it displays: 1111011
| | %B | like %b, but using an uppercase "E", with the # flag | | %p | a pointer (outputs the Perl value’s address in hexadecimal) | | %n | special: *stores* the number of characters output so far into the next variable in the parameter list |
Check my new How To Tutorial eBook (PDF format):to see a lot of fully commented examples that help you use the sprintf function in your scripts.
You may specify several additional attributes between the % and the format letter in order to control the interpretation of the Perl sprintf function format:| Attribute | Meaning, Example | format
parameter
index | By default sprintf will format the next unused argument in the list, but this parameter index, such as 2$, enables you to take the arguments out of order.
my $string = sprintf '%2$d %1$d', 12, 34;
print "$string\n"; # it displays: 34 12
$string = sprintf '%3$d %d %1$d', 1, 2, 3;
print "$string\n"; # it displays: 3 1 1
| flags one
or more
of:space
+
-
0
#
|
prefix non-negative number with a space
prefix non-negative number with a plus sign
left-justify within the field
use zeros, not spaces, to right-justify
ensure the leading "0" for any octal,
prefix non-zero hexadecimal with "0x" or "0X",
prefix non-zero binary with "0b" or "0B" | | vector flag | It tells Perl to interpret the supplied string as a vector of integers, one for each character in the string.
Perl applies the format to each integer in turn, then joins the resulting string with a separator (a dot . by default).
If you put an asterisk * before the v you can override the string to use to separate the numbers:
my $string = sprintf "%*vd", ":", "AB\x{100}";
print "$string\n"; # it displays 65:66:256
| | (minimum) width | Arguments are usually formatted to be as wide as required todisplay the given value, but you can override the width by putting a number here, or get the width from the next argument (with *):
my $string = sprintf "%5s", "a";
print "$string\n"; # it displays " a"
$string = sprintf "%*s", 5, "a";
print "$string\n"; # it displays " a"
| | precision, or maximum width | You can specify a precision (for numeric conversions) or a maximum width (for string conversions) by specifying a dot . followed by a number.
For floating-point formats (excepting g or G) this specifies how many places right of the decimal point to show:
my $string = sprintf "%.2f", 123.4567;
print "$string\n"; # it displays: 123.46
$string = sprintf "%.5s", "language";
print "$string\n"; # it displays: langu
| | size | For numeric conversions, you can specify the size to interpret thenumber as using l, h, V, q, L or ll. So: l - interpret integer as C type "long" or "unsigned long"
h - interpret integer as C type "short" or "unsigned short" or quads (typically 64-bit integers)
q, L or ll - interpret integer as C type "long long", "unsigned long long" or "quads" (typically 64-bit integers) | | order of arguments | You can use * to require additional arguments, these are consumed from the argument list in the order they appear in the format specification before the value to format:
my $val = 1234.12345;
my $string = sprintf "%*.*s", 9, 7, $val;
print "$string\n"; # it displays: " 1234.12"
In the above example, 9 is uses for the width, 7 for the precision, and $val as the value to format. |
Du you want to see more examples? Check my new "Perl Scalar and String Functions - How To Tutorial eBook" to see other examples about how to use the Perl sprintf function in your scripts:- How to use the Perl sprintf function to convert from decimal to hexadecimal
- How to use the Perl sprintf function to convert from decimal to octal
- How to use the Perl sprintf function to pad a string with blanks
- How to use the Perl sprintf function to format floating-point numbers
- How to use the Perl sprintf function with regex
- How to use the Perl sprintf function to pad a number on the left with zeroes
- How to use the Perl sprintf function to expand variables in text strings
and much more.
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Perl How To Tutorial eBooks
Table of Contents:
A Perl Script
Install Perl
Running Perl
Perl Data Types
Perl Variables
Perl Operators
Perl Lists
Perl Arrays
Array Size
Array Length
Perl Hashes
Perl Statements
Perl if
Perl unless
Perl switch
Perl while
Perl do-while
Perl until
Perl do-until
Perl for
Perl foreach
Built-in Perl Functions
Functions by Category
String Functions
List Functions
Array Functions
Hash Functions
Miscellaneous Functions
Functions in alphabetical order
chomp
chop
chr
crypt
defined
delete
each
grep
hex
index
join
lc
lcfirst
length
map
oct
ord
pack
pop
push
q
qq
qw
reverse
rindex
scalar
shift
sort
splice
split
sprintf
substr
tr
uc
ucfirst
undef
unshift
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