printf (awk,perl,shell) float rounding issue Post: 302715123

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Top Forums Shell Programming and Scripting printf (awk,perl,shell) float rounding issue Post 302715123 by elixir_sinari on Saturday 13th of October 2012 11:35:25 PM

10-14-2012

Registered User

printf (awk,perl,shell) float rounding issue

Hi guys,

could someone throw some light on the following behaviour of printf (I'll start with info about the system and the tool/shell/interpreter versions)?:

Code:

$ uname -a
Linux linux-86if.site 3.1.0-1.2-desktop #1 SMP PREEMPT Thu Nov 3 14:45:45 UTC 2011 (187dde0) x86_64 x86_64 x86_64 GNU/Linux

$ bash --version
GNU bash, version 4.2.10(1)-release (x86_64-suse-linux-gnu) 

$ awk --version
GNU Awk 4.0.0 

$ perl --version
This is perl 5, version 14, subversion 2 (v5.14.2) built for x86_64-linux-thread-multi 

$ ksh ### using ksh now
$ echo ${.sh.version}
Version JM 93t+ 2010-06-21 

$ exit ### back to bash

$ type printf
printf is a shell builtin

$ printf "%.0f\n" 4.5
4

$ printf "%.0f\n" 5.5
6

$ awk 'BEGIN{printf "%.0f\n",4.5}'
4

$ awk 'BEGIN{printf "%.0f\n",5.5}'
6

$ perl -e 'printf "%.0f\n",4.5'
4

$ perl -e 'printf "%.0f\n",5.5'
6

$ ksh ### now to ksh
$ whence -v printf
printf is a shell builtin

$ printf "%.0f\n" 4.5
5

$ printf "%.0f\n" 5.5
6

Only the printf builtin in ksh93t+ seems to give me what I expect (4.5 being rounded to 5 and 5.5 to 6).

Why so? And if this has anything to do with the internal representation of numbers, why does ksh93t+ make an exception?

Last edited by elixir_sinari; 10-14-2012 at 12:48 AM..

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LEARN ABOUT X11R4

printf

PRINTF(1)                                                          User Commands                                                         PRINTF(1)

NAME

       printf - format and print data

SYNOPSIS

       printf FORMAT [ARGUMENT]...
       printf OPTION

DESCRIPTION

       Print ARGUMENT(s) according to FORMAT, or execute according to OPTION:

       --help display this help and exit

       --version
              output version information and exit

       FORMAT controls the output as in C printf.  Interpreted sequences are:

       "     double quote

       \     backslash

       a     alert (BEL)

            backspace

       c     produce no further output

       e     escape

       f     form feed

       
     new line

       
     carriage return

       	     horizontal tab

       v     vertical tab

       NNN   byte with octal value NNN (1 to 3 digits)

       xHH   byte with hexadecimal value HH (1 to 2 digits)

       uHHHH Unicode (ISO/IEC 10646) character with hex value HHHH (4 digits)

       UHHHHHHHH
              Unicode character with hex value HHHHHHHH (8 digits)

       %%     a single %

       %b     ARGUMENT as a string with '' escapes interpreted, except that octal escapes are of the form  or NNN

       %q     ARGUMENT  is  printed  in  a format that can be reused as shell input, escaping non-printable characters with the proposed POSIX $''
              syntax.

       and all C format specifications ending with one of diouxXfeEgGcs, with ARGUMENTs converted to proper type first.  Variable widths are  han-
       dled.

       NOTE:  your  shell  may  have its own version of printf, which usually supersedes the version described here.  Please refer to your shell's
       documentation for details about the options it supports.

AUTHOR

       Written by David MacKenzie.

REPORTING BUGS

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
       Report printf translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2017 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       printf(3)

       Full documentation at: <http://www.gnu.org/software/coreutils/printf>
       or available locally via: info '(coreutils) printf invocation'

GNU coreutils 8.28                                                 January 2018                                                          PRINTF(1)

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