printf(1) USER COMMANDS 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 specifica-
tions 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 specif-
ications, each of which results in fetching zero
or more args; and 3) C-language escape sequences,
which are translated into the corresponding char-
acters.
arg string(s) to be printed under the control of for-
mat. 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 con-
verted. If this field is not provided, the arg follow-
ing the last arg converted is used.
An optional decimal digit string specifying a minimum
field width. If the converted value has fewer charac-
ters 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 conver-
sion. 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 speci-
fied by the field width. That is, if precision is
specified, its value is used to control the number of
characters printed.
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printf(1) USER COMMANDS printf(1)
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 preci-
sion. The arg 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 preci-
sion 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
.
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printf(1) USER COMMANDS printf(1)
SEE ALSO
printf(3S) in the Programmer's Reference Manual.
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