Very often on unix environment we have to deal with symlinks (aka soft links – reference to other files).<\/p>\n
Because of different reason the referenced file may be moved or removed, but the\u00a0 symlink still points to the old file.<\/p>\n
\nSuch situations can lead to unexpected errors: e.g if your symlink points to an executable and the referenced file was deleted then you will get “Permission denied” message, and you will ask yourself: why it does not work ,couple of days ago it was just fine; and the file is there ?!.<\/p>\n
Because of this few years ago I’ve made a small script to look for dead links. \nWhat is doing this script:<\/p>\n In a few words: it is a recursive search down into the hierarchy.\n<\/p>\n \nThere is just one interesting thing, because of the symlinks there are chances to have cycles in the files structure. \nThe solution is to keep track of all the already scanned directories, and when they are found 2nd<\/sup> time, they will be ignored – this can be done using other hash (aka associative array). \nHere is the dead_links.pl<\/a> , and bellow is the code (just copy->paste the code if the download link has problems)\n<\/p>\n Feedback<\/a> is appreciated, comments appreciated too.<\/p>\n Very often on unix environment we have to deal with symlinks (aka soft links – reference to other files). Because of different reason the referenced file may be moved or removed, but the\u00a0 symlink still points to the old file. Such situations can lead to unexpected errors: e.g if your symlink points to an executable … Read Full Article<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,5,7],"tags":[11,10,12,14,15,16,13],"class_list":["post-16","post","type-post","status-publish","format-standard","hentry","category-perl","category-programming","category-unix","tag-dead","tag-find","tag-links","tag-linux-2","tag-perl-2","tag-recursive","tag-unix-2","category-6-id","category-5-id","category-7-id","post-seq-1","post-parity-odd","meta-position-corners","fix"],"_links":{"self":[{"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/posts\/16","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/comments?post=16"}],"version-history":[{"count":21,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/posts\/16\/revisions"}],"predecessor-version":[{"id":273,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/posts\/16\/revisions\/273"}],"wp:attachment":[{"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/media?parent=16"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/categories?post=16"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/notnull.ro\/log\/wp-json\/wp\/v2\/tags?post=16"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nUsually I start this script during weekend, and Monday morning I’m just looking on the reports.
\n
\nI want it to run on different Unix flavors, so I’ve choose something portable: JAVA<\/del> Perl .\n<\/p>\n\n
\n
\nAnd it means that with this algorithm we may enter into a never ending loop.\n<\/p>\n
\nWe will not keep in this hash the name\/path of the directory because we can also have hard links of the files (to paths pointing to the same “content”), and because of this we need some info which unique identifies the files\/directories content.
\nAnd this info is provided by stat($file)<\/em> Perl routine.
\nstat() return a lot of things, but we are interested only in first 2 elements: device number of files system and the inode number.
\nThey unique identify the files.\n<\/p>\n\r\n\r\n#!\/usr\/local\/bin\/perl\r\n# search for dead symlinks into hierarchy\r\n# author marcel_preda[at]yahoo.com\r\n\r\n\r\nuse strict ;\r\n# a global hash with dead links\r\nmy %DeadLinks = ();\r\n\r\n# a global with the visited dev-inodes \r\nmy %DevInodes = ();\r\n\r\n\r\n# print a short help\r\n# every `pro' script should have something like this\r\nsub printUse\r\n{\r\n\tprint <<EOF;\r\n\\nUse\t`$0 [Options]'\r\n\t`$0 [directoryName]'\r\n\tValid options:\r\n\t\t-h, --help print this help ;\r\n\r\nEOF\r\n\texit 0;\r\n}\r\n\r\n\r\n# search (and print) in a subdirectory\r\nsub searchLinks\r\n{\r\n# the global %DeadLinks, %DevInodes variables will be used in this subroutine\r\n\r\n\tmy($file,@files,@files2);\r\n\tmy ($dev, $inode) = stat($_[0]);\r\n\t# $dev:$inode identifies the file \r\n\tif ($DevInodes{\"$dev:$inode\"}){\r\n\t\t# directory was already visited, probable a cyclic link or hard link\r\n\t\t# print \"VISITED: \", $_[0], \" \\n\";\r\n\t\treturn; \r\n\t};\r\n\r\n\t#mark dir as visited to not scan it next time\r\n\t$DevInodes{\"$dev:$inode\"} = 1;\r\n\r\n\tif (opendir(DIR_HANDLE,$_[0])){\r\n\t\twhile ($file=readdir(DIR_HANDLE)) {\r\n\t\t\tpush(@files,\"$_[0]\/$file\");\r\n\t\t};\r\n\t\tclosedir(DIR_HANDLE);\r\n\t\t@files2=grep((!\/\\.\\.?$\/),@files);\t#skip `.' and `..' dirs\r\n\t\tfor $file (@files2){\r\n\t\t\t# if link, check if it is not a dead one\r\n\t\t\tif ( -l $file ) {\r\n\t\t\t\t($dev, $inode) = stat $file;\r\n\t\t\t\tif ((! $dev) && (! $inode)){\r\n\t\t\t\t\t$DeadLinks{$file} = readlink $file;\r\n\t\t\t\t};\r\n\t\t\t};\r\n\t\t\t\t\r\n\t\t\t# if is directory call again the subrutine\r\n \tsearchLinks($file) if (-d $file) ;\r\n\t\t}\r\n\t};\r\n}\r\n\r\n#main\r\nmy $DIR=$ARGV[0];\r\n\r\n# print help\r\nwhile ( $_ = shift ){\r\n\t(\/^-h$\/ || \/^-+help$\/ ) && printUse(); \r\n};\r\n\r\n# no dir provided, use the $PWD\r\nunless ($DIR) {$DIR='.';};\r\n\r\nsearchLinks($DIR);\r\n\r\n# Report dead links\r\nmy $link;\r\nforeach $link (keys %DeadLinks){\r\n print 'DEAD LINK', \"\\t $link\\t->\\t\", $DeadLinks{$link}, \"\\n\";\r\n};\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"