printf(1) (man pages section 1: User Commands)

man pages section 1: User Commands

printf(1)

NAME

printf– write formatted output

SYNOPSIS

printf

format

argument

DESCRIPTION

The printf command writes formatted operands to the standard output. The argument operands are formatted under control of the format operand.

OPERANDS

The following operands are supported:

format

A string describing the format to use to write the remaining operands. The format operand is used as the format string described on the formats(5) manual page, with the following exceptions:

A SPACE character in the format string, in any context other than a flag of a conversion specification, is treated as an ordinary character that is copied to the output.
A character in the format string is treated as a character, not as a SPACE character.
In addition to the escape sequences described on the formats(5) manual page (\\, \a, \b, \f, \n, \r, \t, \v), \ddd, where ddd is a one-, two- or three-digit octal number, is written as a byte with the numeric value specified by the octal number.
The program does not precede or follow output from the d or u conversion specifications with blank characters not specified by the format operand.
The program does not precede output from the o conversion specification with zeros not specified by the format operand.
An additional conversion character, b, is supported as follows. The argument is taken to be a string that may contain backslash-escape sequences. The following backslash-escape sequences are supported:
- the escape sequences listed on the formats(5) manual page (\\, \a, \b, \f, \n, \r, \t, \v), which are converted to the characters they represent
- \0ddd, where ddd is a zero-, one-, two- or three-digit octal number that is converted to a byte with the numeric value specified by the octal number
- \c, which is written and causes printf to ignore any remaining characters in the string operand containing it, any remaining string operands and any additional characters in the format operand.

The interpretation of a backslash followed by any other sequence of characters is unspecified.

Bytes from the converted string are written until the end of the string or the number of bytes indicated by the precision specification is reached. If the precision is omitted, it is taken to be infinite, so all bytes up to the end of the converted string are written. For each specification that consumes an argument, the next argument operand is evaluated and converted to the appropriate type for the conversion as specified below. The format operand is reused as often as necessary to satisfy the argument operands. Any extra c or s conversion specifications are evaluated as if a null string argument were supplied; other extra conversion specifications are evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified. If a character sequence in the format operand begins with a % character, but does not form a valid conversion specification, the behavior is unspecified.

argument

The strings to be written to standard output, under the control of format. The argument operands are treated as strings if the corresponding conversion character is b, c or s. Otherwise, it is evaluated as a C constant, as described by the ISO C standard, with the following extensions:

A leading plus or minus sign is allowed.
If the leading character is a single- or double-quote, the value is the numeric value in the underlying codeset of the character following the single- or double-quote.

If an argument operand cannot be completely converted into an internal value appropriate to the corresponding conversion specification, a diagnostic message is written to standard error and the utility does not exit with a zero exit status, but continues processing any remaining operands and writes the value accumulated at the time the error was detected to standard output.

USAGE

Notice that this printf utility, like the printf(3C) function on which it is based, makes no special provision for dealing with multi-byte characters when using the %c conversion specification or when a precision is specified in a %b or %s conversion specification. Applications should be extremely cautious using either of these features when there are multi-byte characters in the character set.

Field widths and precisions cannot be specified as *.

For compatibility with previous versions of SunOS 5.x, the $ format specifier is supported for formats containing only %s specifiers.

The %b conversion specification is not part of the ISO C standard; it has been added here as a portable way to process backslash escapes expanded in string operands as provided by the echo utility. See also the USAGE section of the echo(1) manual page for ways to use printf as a replacement for all of the traditional versions of the echo utility.

If an argument cannot be parsed correctly for the corresponding conversion specification, the printf utility reports an error. Thus, overflow and extraneous characters at the end of an argument being used for a numeric conversion are to be reported as errors.

It is not considered an error if an argument operand is not completely used for a c or s conversion or if a string operand's first or second character is used to get the numeric value of a character.

EXAMPLES

Example 1 Printing a series of prompts

To alert the user and then print and read a series of prompts:

example% printf "\aPlease fill in the following: \nName: "
read name
printf "Phone number: "
read phone

Example 2 Printing a table of calculations

To read out a list of right and wrong answers from a file, calculate the percentage correctly, and print them out. The numbers are right-justified and separated by a single tab character. The percentage is written to one decimal place of accuracy:

example% while read right wrong ; do
   percent=$(echo "scale=1;($right*100)/($right+$wrong)" | bc)
   printf "%2d right\t%2d wrong\t(%s%%)\n" \
	   $right $wrong $percent
done < database_file

Example 3 Printing number strings

The command:

example% printf "%5d%4d\n" 1 21 321 4321 54321

produces:

    1  21
  3214321
54321   0

Notice that the format operand is used three times to print all of the given strings and that a 0 was supplied by printf to satisfy the last %4d conversion specification.

Example 4 Tabulating conversion errors

The printf utility tells the user when conversion errors are detected while producing numeric output; thus, the following results would be expected on an implementation with 32-bit twos-complement integers when %d is specified as the format operand:

Arguments	Standard	Diagnostic
5a	5	printf: 5a not completely converted
9999999999	2147483647	printf: 9999999999: Results too large
-9999999999	-2147483648	printf: -9999999999: Results too large
ABC	0	printf: ABC expected numeric value

Notice that the value shown on standard output is what would be expected as the return value from the function strtol(3C). A similar correspondence exists between %u and strtoul(3C), and %e, %f and %g and strtod(3C).

Example 5 Printing output for a specific locale

In a locale using the ISO/IEC 646:1991 standard as the underlying codeset, the command:

example% printf "%d\n" 3 +3 -3 \'3 \"+3 "'-3"

produces:

`3`	Numeric value of constant 3
`3`	Numeric value of constant 3
`-3`	Numeric value of constant -3
`51`	Numeric value of the character `3' in the ISO/IEC 646:1991 standard codeset
`43`	Numeric value of the character `+' in the ISO/IEC 646:1991 standard codeset
`45`	Numeric value of the character `-' in the SO/IEC 646:1991 standard codeset

Notice that in a locale with multi-byte characters, the value of a character is intended to be the value of the equivalent of the wchar_t representation of the character.

If an argument operand cannot be completely converted into an internal value appropriate to the corresponding conversion specification, a diagnostic message is written to standard error and the utility does exit with a zero exit status, but continues processing any remaining operands and writes the value accumulated at the time the error was detected to standard output.

ENVIRONMENT VARIABLES

See environ(5) for descriptions of the following environment variables that affect the execution of printf: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, and NLSPATH.

EXIT STATUS

The following exit values are returned:

0: Successful completion.
>0: An error occurred.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Availability	SUNWloc
CSI	enabled
Interface Stability	Standard