/[autoepatch]/trunk/doc/howitworks.docbook
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Revision 28 Revision 29
142 </varlistentry> 142 </varlistentry>
143</variablelist> 143</variablelist>
144 144
145</sect1> 145</sect1>
146 146
147<sect1 id="whitespaces">
148<title>Whitespaces handling and safety</title>
149
150<para>
151While there are currently some limitations in ebuilds and in Portage
152code that disallow using paths with spaces for important directories
153like the merge root, the temporary directory and the portage tree
154directory, autoepatch was supposed not to break even if all of them had
155all kind of special characters. Unfortunately this is not always
156possible, because of limitations in the tools and the language used.
157</para>
158
159<para>
160The biggest limitation is provided by bash itself: variables cannot
161contain the NULL character, which means that the targets cannot be
162passed with the output of find -print0 or grep -Z, so the targets
163have to be separated by the \n sequence (new line).
164</para>
165
166<para>
167To try minimising the possibility of problems during piping throught
168different commands (find, grep and so on), it is suggested to use the
169option <emphasis>find $dir -exec cmd {} +</emphasis> rather than using
170-print and xargs (this also avoids one process spawn), and if you need
171to pass the result of grep -l, also add the --null parameter.
172</para>
173
174<warning>
175 <para>
176 For reasons far from our understanding, FreeBSD people decided to
177 use the -Z option to GNU grep to support running grep over
178 gzip-compressed files. For compatibility and portability, rather
179 than using the -Z option, you should use the --null option in
180 autoepatch patchsets, which would behave consistently on both Linux
181 and non-Linux systems.
182 </para>
183</warning>
184
185</sect1>
186
147<sect1 id="prefixsupport"> 187<sect1 id="prefixsupport">
148<title>Alternative prefixes support</title> 188<title>Alternative prefixes support</title>
149 189
150<para> 190<para>
151Although Portage, at the time of writing, it's limited to work as a 191Although Portage, at the time of writing, it's limited to work as a

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