NAME

printf − Writes formatted output

SYNOPSIS

printf format [argument ...]

DESCRIPTION

The printf command converts, formats, and writes its arguments to the standard output. The values specified by the argument variable are formatted under control of the format variable. 

Syntax of the argument Variable

The argument variable is a list of one or more strings to be written to the standard output under the control of the format variable.  These are treated as strings if the corresponding conversion character is b, c, or s; otherwise, it is evaluated as a C constant, with the following extensions:

A leading + (plus sign) or - (minus sign) is allowed. 

If the leading character is a ’ (single quote) or " (double quote), the value is the numeric value in the underlying code set of the character following the single quote or double quote. 

Syntax of the format Variable

The format variable is a character string that contains three types of objects:

       •Plain characters that are copied to the output stream. 

       •The following escape sequences are both copied to the output stream and cause the associated action to occur on display devices that are capable of the action. 

\\Backslash

\aAlert

\bBackspace

\fFormfeed

\nNewline

\rCarriage Return

\tTab

\vVertical Tab

\dddWhere ddd is a one-, two-, or three-digit octal number.  These escape sequences are displayed as a byte with the numeric value specified by the octal number. 

       •A delta character in the format string is treated as a delta character, rather than as a space character. 

The format variable is reused as often as necessary to satisfy the arguments. 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. 

Each conversion specification in the format variable has the following syntax:

     1.A % (percent sign). 

     2.Zero or more options, which modify the meaning of the conversion specification.  The option characters and their meanings are as follows:

-The result of the conversion is left aligned within the field. 

+The result of a signed conversion always begins with a + (plus) or - (minus). 

blankIf the first character of a signed conversion is not a sign, a blank is prefixed to the result. If both the blank and + options appear, then the blank option is ignored. 

#The value is converted to an alternative form.  For c, d, i, u, and s conversions, the option has no effect. For o conversion, it increases the precision to force the first digit of the result to be a 0 (zero). For x and X conversions, a nonzero result has 0x, or 0X prefixed to it, respectively.  For e, E, f, g, and G conversions, the result always contains a radix character, even if no digits follow the radix character. For g and G conversions, trailing zeros are not removed from the result as they usually are. 

0For d, i, o, u, x, X, e, E, f, g, and G conversions, leading zeros (following any indication of sign or base) are used to pad to the field width, no space padding is performed.  If the 0 (zero) and - options appear, the 0 (zero) option is ignored. For d, i, o, u, x, and X conversions, if a precision is specified, the 0 (zero) option is ignored. 

     3.An optional decimal digit string that specifies the minimum field width. If the converted value has fewer characters than the field width, the field is padded on the left to the length specified by the field width. If the left-adjustment option flag (-) is specified, the field is padded on the right. 

     4.An optional precision. The precision is a . (dot) followed by an asterisk (∗), or a decimal digit string. If no precision is given, it is treated as 0 (zero).  The precision specifies:

       •The minimum number of digits to appear for the d, o, i, u, x, or X conversions. 

       •The number of digits to appear after the radix character for the e and f conversions. 

       •The maximum number of significant digits for the g conversion. 

       •The maximum number of bytes to be printed from a string in the s conversion. 

     5.A character that indicates the type of conversion to be applied, as follows:

%Performs no conversion. Prints a % (percent sign). 

bAccepts a value as a string that may contain backslash-escape sequences. Bytes from the converted string are printed until the end of the string or number of bytes indicated by the precision specification is reached. If the precision is omitted, all bytes until the first null character are printed. 

The following backslash-escape sequences are supported:

       •The \Oddd sequence, 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. 

       •The escape sequences previously listed under the description of the format variable. These are converted to the individual characters they represented. 

       •The \c sequence, which is not displayed and causes the printf command to ignore any remaining characters in the string parameter containing it, any remaining string parameters, and any additional characters in the format variable. 

cPrints the first character of the argument. 

d, iAccepts an integer value and converts it to a signed decimal notation in the style [-]dddd.  The precision specifies the minimum number of digits to appear. If the value being converted can be represented in fewer digits, it is expanded with leading zeros. The default precision is 1. The result of converting a 0 (zero) value with a precision of 0 (zero) is a null string. Specifying a field width with a 0 (zero) as a leading character causes the field width value to be padded with leading zeros. 

e, EAccepts a float or double value and converts it to the exponential form [-] d.dde +|- dd. There is one digit before the radix character (shown here as the decimal point), and the number of digits after the radix character is equal to the precision specification. The LC_NUMERIC locale category determines the radix character to use in this format. If no precision is specified, then six digits are output. If the precision is 0 (zero), then no radix character appears.  The E conversion character produces a number with E instead of e before the exponent. The exponent always contains at least two digits. However, if the value to be printed requires an exponent greater than two digits, additional exponent digits are printed as necessary. 

fAccepts a float or double value and converts it to decimal notation in the format [-] ddd.ddd.  The number of digits after the radix character (shown here as the decimal point) is equal to the precision specification. The LC_NUMERIC locale category determines the radix character to use in this format. If no precision is specified, then six digits are output. If the precision is 0 (zero), then no radix character appears. 

g, GAccepts a float or double value and converts it in the style of the f or e conversion characters (or E in the case of the G conversion), with the precision specifying the number of significant digits.  Trailing zeros are removed from the result. A radix character appears only if it is followed by a digit. The style used depends on the value converted. Style g results only if the exponent resulting from the conversion is less than -4, or if it is greater than or equal to the precision. 

oAccepts an integer value and converts it to unsigned octal notation.  The precision specifies the minimum number of digits to appear. If the value being converted can be represented in fewer digits, it is expanded with leading zeros. The default precision is 1. The result of converting a 0 (zero) value with a precision of 0 (zero) is a null string. Specifying a field width with a 0 (zero) as a leading character causes the field width value to be padded with leading zeros.  An octal value for field width is not implied. 

sAccepts a value as a string, and bytes from the string are printed until the end of the string is encountered or the number of bytes indicated by the precision is reached. If no precision is specified, all characters up to the first null character are printed. 

uAccepts an integer value and converts it to unsigned decimal notation. The precision specifies the minimum number of digits to appear. If the value being converted can be represented in fewer digits, it is expanded with leading zeros. The default precision is 1. The result of converting a 0 (zero) value with a precision of 0 (zero) is a null string. Specifying a field width with a 0 (zero) as a leading character causes the field width value to be padded with leading zeros. 

x, XAccepts an integer value and converts it to unsigned hexadecimal notation. The letters abcdef are used for the x conversion and the letters ABCDEF are used for the X conversion. The precision specifies the minimum number of digits to appear. If the value being converted can be represented in fewer digits, it is expanded with leading zeros. The default precision is 1. The result of converting a 0 (zero) value with a precision of 0 (zero) is a null string. Specifying a field width with a 0 (zero) as a leading character causes the field width value to be padded with leading zeros. 

If the result of a conversion is wider than the field width, the field is expanded to contain the converted result. No truncation occurs.  However, a small precision may cause truncation on the right. 

Environment Variables

The following environment variables control the language applied to the output. 

LANGDetermines the locale to use for the locale categories when neither LC_ALL nor the corresponding environment variable (beginning with LC_) specifies a locale. 

LC_ALL
If set, overrides the values of all other locale variables (LANG or any LC_ environment variable). 

LC_CTYPE
Determines the locale for the interpretation of sequences of bytes of text data as characters; for example, single-byte versus multibyte characters in arguments.

LC_MESSAGE
Determines the language in which diagnostic messages are written to standard error.

LC_NUMERIC
Determines the locale for numbers written using the e, E, f, g, or G conversion characters. 

EXAMPLES

     1.The following printf command formats a series of numbers:

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

This command produces the following output:

    1  21
  3214321
54321   0

The format variable is used three times to print all of the given strings. The 0 (zero) is supplied by the printf command to satisfy the last %4d conversion specification. 

     2.The following script includes printf commands to alert the user (sound a beep) and display prompts for entering a name and phone number.  The script then appends the user entries to a file. 

printf "\aPlease fill in the following: \nName: "
read name
printf "Phone number: "
read phone
echo $name "  " $phone >> phone_list
echo "" >> phone_list

RELATED INFORMATION

Functions: printf(3)