1% Copyright The Numerical Algorithms Group Limited 1992-94. All rights reserved. 2% !! DO NOT MODIFY THIS FILE BY HAND !! Created by ht.awk. 3\newcommand{\FileNameXmpTitle}{FileName} 4\newcommand{\FileNameXmpNumber}{9.25} 5% 6% ===================================================================== 7\begin{page}{FileNameXmpPage}{9.25 FileName} 8% ===================================================================== 9\beginscroll 10 11% 12% 13% 14% 15% 16 17 18 19The \spadtype{FileName} domain provides an interface to the computer's 20file system. 21Functions are provided to manipulate file names and to test properties of 22files. 23 24The simplest way to use file names in the \Language{} interpreter is to 25rely on conversion to and from strings. 26The syntax of these strings depends on the operating system. 27\xtc{ 28}{ 29\spadpaste{fn: FileName \bound{fndecl}} 30} 31\xtc{ 32On AIX, this is a proper file syntax: 33}{ 34\spadpaste{fn := "/spad/src/input/fname.input" \free{fndecl}\bound{fn}} 35} 36 37Although it is very convenient to be able to use string notation 38for file names in the interpreter, it is desirable to have a portable 39way of creating and manipulating file names from within programs. 40\xtc{ 41A measure of portability is obtained by considering a file name 42to consist of three parts: the {\it directory}, the {\it name}, 43and the {\it extension}. 44}{ 45\spadpaste{directory fn \free{fn}} 46} 47\xtc{ 48}{ 49\spadpaste{name fn \free{fn}} 50} 51\xtc{ 52}{ 53\spadpaste{extension fn \free{fn}} 54} 55The meaning of these three parts depends on the operating system. 56For example, on CMS the file \spad{"SPADPROF INPUT M"} 57would have directory \spad{"M"}, name \spad{"SPADPROF"} and 58extension \spad{"INPUT"}. 59 60\xtc{ 61It is possible to create a filename from its parts. 62}{ 63\spadpaste{fn := filename("/u/smwatt/work", "fname", "input") \free{fndecl}\bound{fn1}} 64} 65\xtc{ 66When writing programs, it is helpful to refer to directories via 67variables. 68}{ 69\spadpaste{objdir := "/tmp" \bound{objdir}} 70} 71\xtc{ 72}{ 73\spadpaste{fn := filename(objdir, "table", "spad") \free{fndecl,objdir}\bound{fn2}} 74} 75\xtc{ 76If the directory or the extension is given as an empty string, then 77a default is used. On AIX, the defaults are the current directory 78and no extension. 79}{ 80\spadpaste{fn := filename("", "letter", "") \free{fndecl}\bound{fn3}} 81} 82 83Three tests provide information about names in the file system. 84\xtc{ 85The \spadfunFrom{exists?}{FileName} operation tests whether the named file exists. 86}{ 87\spadpaste{exists? "/etc/passwd"} 88} 89\xtc{ 90The operation \spadfunFrom{readable?}{FileName} tells whether the named file 91can be read. If the file does not exist, then it cannot be read. 92}{ 93\spadpaste{readable? "/etc/passwd"} 94} 95\xtc{ 96}{ 97\spadpaste{readable? "/etc/security/passwd"} 98} 99\xtc{ 100}{ 101\spadpaste{readable? "/etc/passwd"} 102} 103\xtc{ 104Likewise, the operation \spadfunFrom{writable?}{FileName} tells whether the named file 105can be written. 106If the file does not exist, the test is determined 107by the properties of the directory. 108}{ 109\spadpaste{writable? "/etc/passwd"} 110} 111\xtc{ 112}{ 113\spadpaste{writable? "/dev/null"} 114} 115\xtc{ 116}{ 117\spadpaste{writable? "/etc/DoesNotExist"} 118} 119\xtc{ 120}{ 121\spadpaste{writable? "/tmp/DoesNotExist"} 122} 123 124The \spadfunFrom{new}{FileName} operation constructs the name of a new 125writable file. 126The argument sequence is the same as for \spadfunFrom{filename}{FileName}, 127except that the name part is actually a prefix for a constructed 128unique name. 129\xtc{ 130The resulting file is in the specified directory 131with the given extension, and the same defaults are used. 132}{ 133\spadpaste{fn := new(objdir, "xxx", "yy") \free{objdir,fndecl}\bound{fn4}} 134} 135\endscroll 136\autobuttons 137\end{page} 138% 139