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<HTML><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><!-- Created on September, 12 2004 by texi2html 1.64 --><!-- Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author) Karl Berry <karl@freefriends.org> Olaf Bachmann <obachman@mathematik.uni-kl.de> and many others.Maintained by: Olaf Bachmann <obachman@mathematik.uni-kl.de>Send bugs and suggestions to <texi2html@mathematik.uni-kl.de> --><HEAD><TITLE>Autoconf, Automake, and Libtool: Separators and Drive Letters</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: Separators and Drive Letters"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: Separators and Drive Letters"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META NAME="Generator" CONTENT="texi2html 1.64"><script language="Javascript"><!-- // Check the browser version. function checkVersion() { if (navigator.appVersion.charAt(0)>=3) return true; if (navigator.appVersion.charAt(0)>=4) return true; 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There are three placeswhere this has an effect:</P><P><DL COMPACT><DT>the shell command line<DD>Up until Cygwin b20.1, it was possible to refer to drive letter prefixedpaths from the shell using the <SAMP>`//c/path/to/file'</SAMP> syntax to referto the directory root at <SAMP>`C:\path\to\file'</SAMP>. Unfortunately, theWindows kernel confused this with the its own network share notation,causing the shell to pause for a short while to look for a machine named<SAMP>`c'</SAMP> in its network neighbourhood. Since release 1.0 of Cygwin, the<SAMP>`//c/path/to/file'</SAMP> notation now really does refer to a machinenamed <SAMP>`c'</SAMP> from Cygwin as well as from Windows. To refer to driveletter rooted paths on the local machine from Cygwin there is a newhybrid <SAMP>`c:/path/to/file'</SAMP> notation. This notation also works inCygwin b20, and is probably the system you should use.<P>On the other hand, using the new hybrid notation in shell scripts meansthat they won't run on old Cygwin releases. Shell code embedded In<TT>`configure.in'</TT> scripts, should test whether the hybrid notationworks, and use an alternate macro to translate hybrid notation to theold style if necessary.</P><P>I must confess that from the command line I now use the longer<SAMP>`/cygdrive/c/path/to/file'</SAMP> notation, since <KBD>TAB</KBD> completiondoesn't yet work for the newer hybrid notation. It is important to usethe new notation in shell scripts however, or they will fail on the latestreleases of Cygwin.</P><P><DT>shell scripts<DD>For a shell script to work correctly on non-Cygwin developmentenvironments, it needs to be aware of and handle Windows path anddirectory separator and drive letters. The Libtool scripts use thefollowing idiom:<P><TABLE><tr><td> </td><td class=smallexample><FONT SIZE=-1><pre>case "$path" in# Accept absolute paths.[\\/]* | [A-Za-\]:[\\/]*) # take care of absolute paths insert some code here ;;*) # what is left must be a relative path insert some code here ;;esac</FONT></pre></td></tr></table></P><P><DT>source code<DD><A NAME="IDX81"></A>When porting Unix software to Cygwin, this is much less of an issuebecause these differences are hidden beneath the emulation layer, and bythe <CODE>mount</CODE> command respectively; although I have found thatGCC, for example, returns a mixed mode <SAMP>`/'</SAMP> and <SAMP>`\'</SAMP> delimitedinclude path which upsets Automake's dependency tracking on occasion.<P>Cygwin provides convenience functions to convert back and forth betweenthe different notations, which we call <EM>POSIX paths</EM> or path lists,and <EM>WIN32 paths</EM> or path lists:</P><P><A NAME="IDX82"></A><DL><DT><U>Function:</U> int <B>posix_path_list_p</B> <I>(const char *<VAR>path</VAR>)</I><DD>Return <SAMP>`0'</SAMP>, unless <VAR>path</VAR> is a <SAMP>`/'</SAMP> and <SAMP>`:'</SAMP> separatedpath list. The determination is rather simplistic, in that a stringwhich contains a <SAMP>`;'</SAMP> or begins with a single letter followed by a<SAMP>`:'</SAMP> causes the <SAMP>`0'</SAMP> return.</DL></P><P><A NAME="IDX83"></A><DL><DT><U>Function:</U> void <B>cygwin_win32_to_posix_path_list</B> <I>(const char *<VAR>win32</VAR>, char *<VAR>posix</VAR>)</I><DD>Converts the <SAMP>`\'</SAMP> and <SAMP>`;'</SAMP> delimiters in <VAR>win32</VAR>, into theequivalent <SAMP>`/'</SAMP> and <SAMP>`:'</SAMP> delimiters while copying into thebuffer at address <VAR>posix</VAR>. This buffer must be preallocated beforecalling the function.</DL></P><P><A NAME="IDX84"></A><DL><DT><U>Function:</U> void <B>cygwin_conv_to_posix_path</B> <I>(const char *<VAR>path</VAR>, char *<VAR>posix_path</VAR>)</I><DD>If <VAR>path</VAR> is a <SAMP>`\'</SAMP> delimited path, the equivalent, <SAMP>`/'</SAMP>delimited path is written to the buffer at address <VAR>posix_path</VAR>.This buffer must be preallocated before calling the function.</DL></P><P><A NAME="IDX85"></A><DL><DT><U>Function:</U> void <B>cygwin_conv_to_full_posix_path</B> <I>(const char *<VAR>path</VAR>, char *<VAR>posix_path</VAR>)</I><DD>If <VAR>path</VAR> is a, possibly relative, <SAMP>`\'</SAMP> delimited path, theequivalent, absolute, <SAMP>`/'</SAMP> delimited path is written to the bufferat address <VAR>posix_path</VAR>. This buffer must be preallocated beforecalling the function.</DL></P><P><A NAME="IDX86"></A><DL><DT><U>Function:</U> void <B>cygwin_posix_to_win32_path_list</B> <I>(const char *<VAR>posix</VAR>, char *<VAR>win32</VAR>)</I><DD>Converts the <SAMP>`/'</SAMP> and <SAMP>`:'</SAMP> delimiters in <VAR>posix</VAR>, into theequivalent <SAMP>`\'</SAMP> and <SAMP>`;'</SAMP> delimiters while copying into thebuffer at address <VAR>win32</VAR>. This buffer must be preallocated beforecalling the function.</DL></P><P><A NAME="IDX87"></A><DL><DT><U>Function:</U> void <B>cygwin_conv_to_win32_path</B> <I>(const char *<VAR>path</VAR>, char *<VAR>win32_path</VAR>)</I><DD>If <VAR>path</VAR> is a <SAMP>`/'</SAMP> delimited path, the equivalent, <SAMP>`\'</SAMP>delimited path is written to the buffer at address <VAR>win32_path</VAR>.This buffer must be preallocated before calling the function.</DL></P><P><A NAME="IDX88"></A><DL><DT><U>Function:</U> void <B>cygwin_conv_to_full_win32_path</B> <I>(const char *<VAR>path</VAR>, char *<VAR>win32_path</VAR>)</I><DD>If <VAR>path</VAR> is a, possibly relative, <SAMP>`/'</SAMP> delimited path, theequivalent, absolute, <SAMP>`\'</SAMP> delimited path is written to the bufferat address <VAR>win32_path</VAR>. This buffer must be preallocated beforecalling the function.</DL></DL><P>You can use these functions something like this:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>voiddisplay_canonical_path(const char *maybe_relative_or_win32){ char buffer[MAX_PATH]; cygwin_conv_to_full_posix_path(maybe_relative_or_win32, buffer); printf("canonical path for %s: %s\n", maybe_relative_or_win32, buffer);}</pre></td></tr></table></P><P>For your code to be fully portable however, you cannot rely on these Cygwinfunctions as they are not implemented on Unix, or even mingw orDJGPP. Instead you should add the following to a shared header, and becareful to use it when processing and building paths and path lists:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>#if defined __CYGWIN32__ && !defined __CYGWIN__ /* For backwards compatibility with Cygwin b19 and earlier, we define __CYGWIN__ here, so that we can rely on checking just for that macro. */# define __CYGWIN__ __CYGWIN32__#endif#if defined _WIN32 && !defined __CYGWIN__ /* Use Windows separators on all _WIN32 defining environments, except Cygwin. */# define DIR_SEPARATOR_CHAR '\\'# define DIR_SEPARATOR_STR "\\"# define PATH_SEPARATOR_CHAR ';'# define PATH_SEPARATOR_STR ";"#endif#ifndef DIR_SEPARATOR_CHAR /* Assume that not having this is an indicator that all are missing. */# define DIR_SEPARATOR_CHAR '/'# define DIR_SEPARATOR_STR "/"# define PATH_SEPARATOR_CHAR ':'# define PATH_SEPARATOR_STR ":"#endif /* !DIR_SEPARATOR_CHAR */</pre></td></tr></table></P><P>With this in place we can use the macros defined above to write codewhich will compile and work just about anywhere:</P><P><TABLE><tr><td> </td><td class=smallexample><FONT SIZE=-1><pre>char path[MAXBUFLEN];snprintf(path, MAXBUFLEN, "%ctmp%c%s\n", DIR_SEPARATOR_CHAR, DIR_SEPARATOR_CHAR, foo);file = fopen(path, "tw+");</FONT></pre></td></tr></table></P><P><A NAME="Executable Filename Extensions"></A></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Gary V. Vaughan</I> on <I>September, 12 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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