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Add a note about the stupid behaviour of "%c" format.

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apb 2008-05-06 12:01:35 +00:00
parent 2925cedf26
commit 76807ad91e
1 changed files with 25 additions and 2 deletions
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27
usr.bin/printf/printf.1
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@ -1,4 +1,4 @@
.\" $NetBSD: printf.1,v 1.20 2003/08/07 11:15:32 agc Exp $
.\" $NetBSD: printf.1,v 1.21 2008/05/06 12:01:35 apb Exp $
.\"
.\" Copyright (c) 1989, 1990, 1993
.\" The Regents of the University of California. All rights reserved.
@ -32,7 +32,7 @@
.\"
.\" from: @(#)printf.1 8.1 (Berkeley) 6/6/93
.\"
.Dd November 5, 1993
.Dd May 6, 2008
.Dt PRINTF 1
.Os
.Sh NAME
@ -387,3 +387,26 @@ Hexadecimal character constants are restricted to, and should be specified
as, two character constants.
This is contrary to the ISO C standard but
does guarantee detection of the end of the constant.
.Sh NOTES
All formats which treat the
.Ar argument
as a number first convert the
.Ar argument
from its external representation as a character string
to an internal numeric representation, and then apply the
format to the internal numeric representation, producing
another external character string representation.
One might expect the
.Cm \&%c
format to do likewise, but in fact it does not.
.Pp
To convert a string representation of a decimal, octal, or hexadecimal
number into the corresponding character, two nested
.Nm
invocations may be used, in which the inner invocation
converts the input to an octal string, and the outer
invocation uses the octal string as part of a format.
For example, the following command outputs the character whose code
is 0x0A, which is a newline in ASCII:
.Pp
.Dl printf \&"$(printf \&"\e\e%o" \&"0x0A")"