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Full Discussion: Newline in ANSI-C standard functions
Top Forums Programming Newline in ANSI-C standard functions Post 303020314 by Corona688 on Monday 16th of July 2018 02:49:11 PM
Old 07-16-2018
The risk of strcpy is this:

Code:
char buf[8]; // Only room for 8 characters
char very_important_variable_touch_and_the_world_explodes=42;

// More than 8 characters, where does the rest go?
strcpy(buf, "HEY GUYS ALJ AF MY FACE IS A ROTTORN BANANA");

So instead, you can do this:

Code:
char buf[8]; 
char very_important_variable_touch_and_the_world_explodes=42;

strncpy(buf, "HEY GUYS ALJ AF MY FACE IS A ROTTORN BANANA", 8);

Which sets the contents of buf to { 'H','E','Y',' ','G','U','Y','S' } and doesn't destroy the world. But because it ran out of room, it couldn't store the null terminator. Meaning buf[] is not guaranteed to contain a proper string after you do strncpy, so trying to use it as a string could cause undefined results and possibly blow up the world. So to be really safe, you do:

Code:
char buf[8]; 
char very_important_variable_touch_and_the_world_explodes=42;

strncpy(buf, "HEY GUYS ALJ AF MY FACE IS A ROTTORN BANANA", 8);

buf[8-1]='\0';

Which sets buf to { 'H','E','Y',' ','G','U','Y','\0' }, which guarantees the buffer is null-terminated whether strncpy ran out of room or not, and does it all without destroying the world.
These 2 Users Gave Thanks to Corona688 For This Post:
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LEARN ABOUT SUSE

ansi_code

term::ansi::code(n)						 Terminal control					       term::ansi::code(n)

__________________________________________________________________________________________________________________________________________________

NAME

       term::ansi::code - Helper for control sequences

SYNOPSIS

       package require Tcl  8.4

       package require term::ansi::code  ?0.1?

       ::term::ansi::code::esc str

       ::term::ansi::code::escb str

       ::term::ansi::code::define name escape code

       ::term::ansi::code::const name code

_________________________________________________________________

DESCRIPTION

       This package provides commands enabling the definition of control sequences in an easy manner.

       ::term::ansi::code::esc str
	      This command returns the argument string, prefixed with the ANSI escape character, "33."

       ::term::ansi::code::escb str
	      This command returns the argument string, prefixed with a common ANSI escape sequence, "33[".

       ::term::ansi::code::define name escape code
	      This  command defines a procedure name which returns the control sequence code, beginning with the specified escape sequence, either
	      esc, or escb.

       ::term::ansi::code::const name code
	      This command defines a procedure name which returns the control sequence code.

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will undoubtedly contain bugs and other problems.  Please report such in the category term	of
       the  Tcllib  SF	Trackers [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas for enhancements you may have for
       either package and/or documentation.

KEYWORDS

       control, declare, define, terminal

COPYRIGHT

       Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>

term									0.1						       term::ansi::code(n)
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