Macintosh Terminal Pocket Guide

Name

printf — stdin  stdout  - file  -- opt  --help  --version

Synopsis

printf format_string [arguments]

The printf command is an enhanced echo: it prints formatted strings on standard output. It operates much like the C programming language function printf( ), which applies a format string to a sequence of arguments to create some specified output. For example:

➜ printf "User %s is %d years old.\n" sandy 29
User sandy is 29 years old.

The first argument is the format string, which in our example contains two format specifications, %s and %d. The subsequent arguments, sandy and 29, are substituted by printf into the format string and then printed. Format specifications can get fancy with floating-point numbers:

➜ printf "That\'ll be $%0.2f, sir.\n" 3
That'll be $3.00, sir.

It is your responsibility to make sure the number of format specifications (%) equals the number of arguments supplied to printf after the format string. If you have too many arguments, the extras are ignored, and if you have too few, printf assumes default values (0 for numeric formats, an empty string for string formats). Nevertheless, you should treat such mismatches as errors, even though printf is forgiving. If they lurk in your shell scripts, they are bugs waiting to happen.

Format specifications are described in detail on the manpage for the C function printf (see man 3 printf). Here are some useful ones:

%d	Decimal integer
%ld	Long decimal integer
%o	Octal integer
%x	Hexadecimal integer
%f	Floating point
%lf	Double-precision ...