Walk a directory/Recursively: Difference between revisions
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=={{header|Dart}}==
<syntaxhighlight lang="dart">
import 'dart:io' show Directory, Platform, File;
void main(List<String> args) {
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There is more than one way to do this in TXR. A recursive walk could be coded using <code>open-directory</code> and <code>getline</code>. Or FFI could be used to gain access to some platform-specific functions like Microsoft's <code>FindFirstFile</code> and so forth.
===Using <code>ftw</code>===
TXR wraps and exposes the POSIX <code>nftw</code> function, which is demonstrated here. This function encapsulates a tree walk, and uses callbacks to inform the program of visited filesystem tree nodes, and of error situations. We can use a <code>lambda</code> for the code walk, or wrap the invocation of <code>ftw</code> with a macro which hides the <code>lambda</code> syntax.
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A nice approach would be to capture a continuation in the callback, and then obtain the walk elements lazily; alas, capturing a continuation from a C library function's callback is not permitted, because the capture would span foreign stack frames.
===Using <code>glob*</code>===
TXR has a <code>glob*</code> function which, like <code>glob</code> is built on the POSIX C library function. <code>glob*</code> also provides Bash-style brace expansion, as well as the double star pattern, which we can use to find files recursively:
<syntaxhighlight lang="txrlisp">(glob* "**/*.c")</syntaxhighlight>
{{out}}
<syntaxhighlight lang="txrlisp">("args.c" "arith.c" "autoload.c" "buf.c" "cadr.c" "chksum.c" "chksums/crc32.c"
"chksums/md5.c" "chksums/sha1.c" "chksums/sha256.c" "combi.c"
"debug.c" "eval.c" "ffi.c" "filter.c" "ftw.c" "gc.c" "glob.c"
"gzio.c" "hash.c" "itypes.c" "lib.c" "linenoise/example.c" "linenoise/linenoise.c"
"match.c" "mpi/mpi.c" "mpi/mplogic.c" "parser.c" "protsym.c"
"psquare.c" "rand.c" "regex.c" "signal.c" "socket.c" "stream.c"
"struct.c" "strudel.c" "sysif.c" "syslog.c" "termios.c" "time.c"
"tree.c" "txr.c" "unwind.c" "utf8.c" "vm.c")</syntaxhighlight>
=={{header|UNIX Shell}}==
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{{libheader|Wren-pattern}}
{{libheader|Wren-sort}}
<syntaxhighlight lang="
import "./pattern" for Pattern
import "./sort" for Sort
var walk // recursive function
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