Summary:this page is a printf formatting cheat sheet. I originally created this cheat sheet for my own purposes, and then thought I would share it is here.
A cool thing about the formatting syntax was that the specifiers you can use be printf
very similar, if not identical, BETW Een different languages, including C, C + +, Java, Perl, Ruby, Scala, and others. So your printf knowledge are reusable, which is a good thing.
printf formatting with Perl and Java
In this cheat sheet I'll show all the examples using Perl, but at first it might help to see one example using both Perl a nd Java. So, here's a simple Perl printf example to get us started:
printf ("The%s jumped over the%s,%d times", "cow", "Moon", 2);
And here is three different Java printf examples, using different methods that is available to your in the Java Programmi Ng language:
System.out.format ("The%s jumped over the%s,%d times", "cow", "Moon", 2); System.err.format ("The%s jumped over the%s,%d times", "cow", "Moon", 2); String result = String.Format ("The%s jumped over the%s,%d times", "cow", "Moon", 2);
As you can see in so last String.format
example, that's line of code doesn ' t print any output, while the first line prints to Stan Dard output, and the second line prints to standard error.
In the remainder of this document I'll use Perl examples, but again, the actual format specifier strings can is used in MA NY different languages.
printf Format specifiers-summary
Here's a quick summary of the available printf format specifiers:
%c |
Character |
%d |
Decimal (integer) number (base 10) |
%e |
Exponential floating-point number |
%f |
Floating-point number |
%i |
Integer (base 10) |
%o |
Octal number (base 8) |
%s |
A string of characters |
%u |
unsigned decimal (integer) number |
%x |
Number in hexadecimal (base 16) |
%% |
Print a percent sign |
\% |
Print a percent sign |
Controlling integer width with printf
The %3d
specifier means a minimum width of three spaces, which, by default, would be right-justified:
printf ("%3d", 0); |
0 |
printf ("%3d", 123456789); |
123456789 |
printf ("%3d",-10); |
-10 |
printf ("%3d",-123456789); |
-123456789 |
left-justifying printf Integer Output
To left-justify integer output with printf, just add a minus sign ( -
) after %
the symbol, such as this:
printf ("%-3d", 0); |
0 |
printf ("%-3d", 123456789); |
123456789 |
printf ("%-3d",-10); |
-10 |
printf ("%-3d",-123456789); |
-123456789 |
The printf zero-fill option
To zero-fill your printf integer output, just add a zero ( 0
) after %
the symbol, like this:
printf ("%03d", 0); |
000 |
printf ("%03d", 1); |
001 |
printf ("%03d", 123456789); |
123456789 |
printf ("%03d",-10); |
-10 |
printf ("%03d",-123456789); |
-123456789 |
printf integer formatting
As a summary of printf integer formatting, here's a little collection of integer formatting examples. Several different options are shown, including a minimum width specification, left-justified, zero-filled, and also a plus sign for positive numbers.
Description |
Code |
Result |
At least five wide |
printf ("'%5d '", 10); |
' 10 ' |
At least Five-wide, left-justified |
printf ("'%-5d '", 10); |
' 10 ' |
At least Five-wide, zero-filled |
printf ("'%05d '", 10); |
' 00010 ' |
At least five-wide, with a plus sign |
printf ("'%+5d '", 10); |
' +10 ' |
Five-wide, plus sign, left-justified |
printf ("'%-+5d '", 10); |
' +10 ' |
Printf-floating Point numbers
Here is several examples showing how to format floating-point numbers with printf:
Description |
Code |
Result |
Print one position after the decimal |
printf ("'%.1f '", 10.3456); |
' 10.3 ' |
Positions after the decimal |
printf ("'%.2f '", 10.3456); |
' 10.35 ' |
Eight-wide, positions after the decimal |
printf ("'%8.2f '", 10.3456); |
' 10.35 ' |
Eight-wide, four positions after the decimal |
printf ("'%8.4f '", 10.3456); |
' 10.3456 ' |
Eight-wide, positions after the decimal, zero-filled |
printf ("'%08.2f '", 10.3456); |
' 00010.35 ' |
Eight-wide, positions after the decimal, left-justified |
printf ("'%-8.2f '", 10.3456); |
' 10.35 ' |
Printing a much larger number with the That same format |
printf ("'%-8.2f '", 101234567.3456); |
' 101234567.35 ' |
printf string Formatting
Here is several examples that show how to format string output with printf:
Description |
Code |
Result |
A Simple string |
printf ("'%s '", "Hello"); |
' Hello ' |
A string with a minimum length |
printf ("'%10s '", "Hello"); |
' Hello ' |
Minimum length, left-justified |
printf ("'%-10s '", "Hello"); |
' Hello ' |
Summary of Special printf characters
The following character sequences has a special meaning when used as printf format specifiers:
\a |
Audible alert |
\b |
Backspace |
\f |
Form Feed |
\ n |
NewLine, or linefeed |
\ r |
Carriage return |
\ t |
tab |
\v |
Vertical tab |
\\ |
Backslash |
As you can see from that last example, because the backslash character itself are treated specially, you has to print Backslash characters in a row to get one backslash character to appear in your output.
Here is a few examples of how to use these special characters:
Description |
Code |
Result |
Insert a tab character in a string |
printf ("Hello\tworld"); |
Hello World |
Insert a newline character in a string |
printf ("Hello\nworld"); |
Hello World |
Typical use of the newline character |
printf ("Hello world\n"); |
Hello World |
A dos/windows path with backslash characters |
printf ("c:\\windows\\system32\\"); |
C:\Windows\System32\
|
A printf Format Reference page (cheat sheet)