printf(1) (Essential Utilities) printf(1)
NAME
printf - print formatted output
SYNOPSIS
printf format [arg ...]
DESCRIPTION
The printf command converts, formats, and prints its args under
control of the format. It fully supports conversion specifications
for strings (%s descriptor); however, the results are undefined for
the other conversion specifications supported by printf(3S).
format a character string that contains three types of objects:
1) plain characters, which are simply copied to the output
stream; 2) conversion specifications, each of which results
in fetching zero or more args; and 3) C-language escape
sequences, which are translated into the corresponding
characters.
arg string(s) to be printed under the control of format. The
results are undefined if there are insufficient args for
the format. If the format is exhausted while args remain,
the excess args are simply ignored.
Each conversion specification is introduced by the character %.
After the %, the following appear in sequence:
An optional field, consisting of a decimal digit string
followed by a $, specifying the next arg to be converted. If
this field is not provided, the arg following the last arg
converted is used.
An optional decimal digit string specifying a minimum field
width. If the converted value has fewer characters than the
field width, it is padded on the left (or right, if the left-
adjustment flag `-' has been given) to the field width. The
padding is with blanks unless the field width digit string
starts with a zero, in which case the padding is with zeros.
An optional precision that gives the maximum number of
characters to be printed from a string in %s conversion. The
precision takes the form of a period (.) followed by a decimal
digit string; a null digit string is treated as zero (nothing
is printed). Padding specified by the precision overrides the
padding specified by the field width. That is, if precision is
specified, its value is used to control the number of
characters printed.
A field width or precision or both may be indicated by an
asterisk (*) instead of a digit string. In this case, an
integer arg supplies the field width or precision. The arg
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printf(1) (Essential Utilities) printf(1)
that is actually converted is not fetched until the conversion
letter is seen, so the args specifying field width or precision
must appear before the arg (if any) to be converted. A
negative field width argument is taken as a `-' (left-
adjustment) flag followed by a positive field width. If the
precision argument is negative, it is changed to zero (nothing
is printed). In no case does a non-existent or small field
width cause truncation of a field; if the result of a
conversion is wider than the field width, the field is simply
expanded to contain the conversion result.
The conversion characters and their meanings are:
%s The arg is taken to be a string and characters from the string
are printed until a null character (\0) is encountered or the
number of characters indicated by the precision specification
is reached. If the precision is missing, it is taken to be
infinite, so all characters up to the first null character are
printed. A null value for arg yields undefined results.
%% Print a %; no argument is converted.
EXAMPLES
The command
printf '%s %s %s\n' Good Morning World
results in the output:
Good Morning World
The following command produces the same output.
printf '%2$s %s %1$s\n' World Good Morning
Here is an example that prints the first 6 characters of $PATH left-
adjusted in a 10-character field:
printf 'First 6 chars of %s are %-10.6s.\n' $PATH $PATH
If $PATH has the value /usr/bin:/usr/local/bin, then the above
command would print the following output:
First 6 chars of /usr/bin:/usr/local/bin are /usr/b .
SEE ALSO
printf(3S) in the Programmer's Reference Manual.
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