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       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME

       printf — write formatted output

SYNOPSIS

       printf format [argument...]

DESCRIPTION

       The printf utility shall  write  formatted  operands  to  the  standard
       output.  The  argument operands shall be formatted under control of the
       format operand.

OPTIONS

       None.

OPERANDS

       The following operands shall be supported:

       format    A string describing the format to use to write the  remaining
                 operands.  See the EXTENDED DESCRIPTION section.

       argument  The  strings  to  be  written  to  standard output, under the
                 control of format.  See the EXTENDED DESCRIPTION section.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment  variables  shall  affect  the  execution  of
       printf:

       LANG      Provide   a   default   value  for  the  internationalization
                 variables that are unset or null. (See the  Base  Definitions
                 volume  of  POSIX.1‐2008,  Section  8.2, Internationalization
                 Variables the precedence  of  internationalization  variables
                 used to determine the values of locale categories.)

       LC_ALL    If  set  to  a non-empty string value, override the values of
                 all the other internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of  sequences  of
                 bytes of text data as characters (for example, single-byte as
                 opposed to multi-byte characters in arguments).

       LC_MESSAGES
                 Determine the locale that should be used to affect the format
                 and  contents  of  diagnostic  messages  written  to standard
                 error.

       LC_NUMERIC
                 Determine the locale for numeric formatting. It shall  affect
                 the  format  of  numbers  written using the e, E, f, g, and G
                 conversion specifier characters (if supported).

       NLSPATH   Determine the location of message catalogs for the processing
                 of LC_MESSAGES.

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       See the EXTENDED DESCRIPTION section.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       The  format operand shall be used as the format string described in the
       Base  Definitions  volume  of  POSIX.1‐2008,  Chapter  5,  File  Format
       Notation with the following exceptions:

        1. A <space> in the format string, in any context other than a flag of
           a  conversion  specification,  shall  be  treated  as  an  ordinary
           character that is copied to the output.

        2. A  ''  character  in  the  format  string  shall be treated as a ''
           character, not as a <space>.

        3. In addition to the escape sequences shown in the  Base  Definitions
           volume  of  POSIX.1‐2008,  Chapter  5,  File Format Notation ('\\',
           '\a', '\b', '\f', '\n', '\r', '\t', '\v'), "\ddd", where ddd  is  a
           one,  two,  or three-digit octal number, shall be written as a byte
           with the numeric value specified by the octal number.

        4. The implementation shall not precede or follow output from the d or
           u  conversion  specifiers  with <blank> characters not specified by
           the format operand.

        5. The implementation shall not precede output from the  o  conversion
           specifier with zeros not specified by the format operand.

        6. The  a,  A,  e, E, f, F, g, and G conversion specifiers need not be
           supported.

        7. An additional conversion specifier character, b, shall be supported
           as  follows.  The  argument  shall be taken to be a string that may
           contain     <backslash>-escape     sequences.     The     following
           <backslash>-escape sequences shall be supported:

           --  The  escape  sequences listed in the Base Definitions volume of
               POSIX.1‐2008, Chapter 5,  File  Format  Notation  ('\\',  '\a',
               '\b',  '\f',  '\n', '\r', '\t', '\v'), which shall be converted
               to the characters they represent

           --  "\0ddd", where ddd is a zero, one, two,  or  three-digit  octal
               number that shall be converted to a byte with the numeric value
               specified by the octal number

           --  '\c', which shall not be written  and  shall  cause  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 shall be 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 shall  be
           taken  to  be infinite, so all bytes up to the end of the converted
           string shall be written.

        8. For each conversion specification that consumes  an  argument,  the
           next  argument  operand  shall  be  evaluated  and converted to the
           appropriate type for the conversion as specified below.

        9. The format operand shall be reused as often as necessary to satisfy
           the argument operands. Any extra c or s conversion specifiers shall
           be evaluated as if a null  string  argument  were  supplied;  other
           extra  conversion  specifications  shall  be 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.

       10. If a character sequence in the format operand  begins  with  a  '%'
           character,  but does not form a valid conversion specification, the
           behavior is unspecified.

       11. The argument  to  the  c  conversion  specifier  can  be  a  string
           containing  zero  or  more bytes. If it contains one or more bytes,
           the first byte shall be written and any additional bytes  shall  be
           ignored.  If  the  argument  is  an empty string, it is unspecified
           whether nothing is written or a null byte is written.

       The argument operands shall be treated as strings if the  corresponding
       conversion specifier is b, c, or s, and shall be evaluated as if by the
       strtod() function if the corresponding conversion specifier is a, A, e,
       E,  f,  F, g, or G.  Otherwise, they shall be evaluated as unsuffixed C
       integer constants,  as  described  by  the  ISO C  standard,  with  the
       following extensions:

        *  A leading <plus-sign> or minus-sign shall be allowed.

        *  If  the  leading  character  is a single-quote or double-quote, the
           value shall be the numeric value in the underlying codeset  of  the
           character following the single-quote or double-quote.

        *  Suffixed integer constants may be allowed.

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

       It is not considered an error if an argument operand is not  completely
       used for a c or s conversion.

EXIT STATUS

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       The floating-point formatting conversion specifications of printf() are
       not required because all arithmetic in the shell is integer arithmetic.
       The  awk  utility performs floating-point calculations and provides its
       own printf function. The bc  utility  can  perform  arbitrary-precision
       floating-point  arithmetic,  but  does not provide extensive formatting
       capabilities. (This printf utility cannot really be used to  format  bc
       output;  it  does not support arbitrary precision.) Implementations are
       encouraged to support the floating-point conversions as an extension.

       Note that this printf utility, like the printf()  function  defined  in
       the  System  Interfaces  volume  of  POSIX.1‐2008 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.

       No provision is made in this volume of POSIX.1‐2008 which allows  field
       widths  and  precisions  to  be  specified  as '*' since the '*' can be
       replaced  directly  in  the  format  operand   using   shell   variable
       substitution.  Implementations  can  also  provide  this  feature as an
       extension if they so choose.

       Hexadecimal character constants as defined in the  ISO C  standard  are
       not recognized in the format operand because there is no consistent way
       to detect the end  of  the  constant.  Octal  character  constants  are
       limited  to,  at  most,  three  octal digits, but hexadecimal character
       constants are only terminated by  a  non-hex-digit  character.  In  the
       ISO C  standard,  the  "##"  concatenation  operator  can  be  used  to
       terminate a constant and follow it with a hexadecimal character  to  be
       written.  In  the shell, concatenation occurs before the printf utility
       has a chance to parse the end of the hexadecimal constant.

       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  APPLICATION  USAGE  section  of  echo  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 is required to report an
       error. Thus, overflow and  extraneous  characters  at  the  end  of  an
       argument  being  used  for  a  numeric  conversion shall be reported as
       errors.

EXAMPLES

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

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

       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>.  The percentage  is  written
       to one decimal place of accuracy:

           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

       The command:

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

       produces:

               1  21
             3214321
           54321   0

       Note  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.

       The  printf  utility  is  required  to  notify 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:

       ┌────────────┬─────────────┬───────────────────────────────────────────┐
       │            │  Standard   │                                           │
       │ ArgumentOutputDiagnostic Output             │
       ├────────────┼─────────────┼───────────────────────────────────────────┤
       │5a          │ 5           │ printf: "5a" not completely converted     │
       │9999999999  │ 2147483647  │ printf: "9999999999" arithmetic overflow  │
       │−9999999999 │ −2147483648 │ printf: "−9999999999" arithmetic overflow │
       │ABC         │ 0           │ printf: "ABC" expected numeric value      │
       └────────────┴─────────────┴───────────────────────────────────────────┘
       The diagnostic message format is  not  specified,  but  these  examples
       convey  the  type of information that should be reported. Note that the
       value shown on standard output is what would be expected as the  return
       value  from  the  strtol() function as defined in the System Interfaces
       volume of POSIX.1‐2008. A similar correspondence exists between %u  and
       strtoul()  and %e, %f, and %g (if the implementation supports floating-
       point conversions) and strtod().

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

           printf "%d\n" 3 +33 \'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 ISO/IEC 646:1991
             standard codeset

       Note 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 as described in the  System  Interfaces
       volume of POSIX.1‐2008.

RATIONALE

       The  printf  utility  was  added  to  provide  functionality  that  has
       historically been provided by echo.   However,  due  to  irreconcilable
       differences in the various versions of echo extant, the version has few
       special features, leaving those to this new printf  utility,  which  is
       based on one in the Ninth Edition system.

       The  EXTENDED  DESCRIPTION  section almost exactly matches the printf()
       function in the ISO C standard, although it is described  in  terms  of
       the   file   format   notation   in  the  Base  Definitions  volume  of
       POSIX.1‐2008, Chapter 5, File Format Notation.

       Earlier versions of this standard  specified  that  arguments  for  all
       conversions other than b, c, and s were evaluated in the same way (as C
       constants, but with stated exceptions). For implementations  supporting
       the  floating-point  conversions  it  was  not  clear  whether  integer
       conversions need  only  accept  integer  constants  and  floating-point
       conversions  need only accept floating-point constants, or whether both
       types of conversions should accept both types of constants. Also by not
       distinguishing  between  them,  the  requirement  relating to a leading
       single-quote or double-quote applied to floating-point conversions even
       though  this  provided no useful functionality to applications that was
       not already available through  the  integer  conversions.  The  current
       standard  clarifies  the situation by specifying that the arguments for
       floating-point conversions are evaluated as if  by  strtod(),  and  the
       arguments for integer conversions are evaluated as C integer constants,
       with the special treatment of  leading  single-quote  and  double-quote
       applying only to integer conversions.

FUTURE DIRECTIONS

       None.

SEE ALSO

       awk, bc, echo

       The  Base  Definitions  volume  of POSIX.1‐2008, Chapter 5, File Format
       Notation, Chapter 8, Environment Variables

       The System Interfaces volume of POSIX.1‐2008, fprintf(), strtod()

COPYRIGHT

       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  7,  Copyright  (C)  2013  by  the  Institute  of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.unix.org/online.html .

       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files    to   man   page   format.   To   report   such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .