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Symbolic Links

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symbolic links

cmd:lndir

SYNOPSIS

lndir [ -silent ] [ -ignorelinks ] [ -withrevinfo ] fromdir [ todir ]

Caution: as opposed to cp, lndir will not create a dir, ie, all dir/files from the 'fromdir' will be created under pwd unless the 'todir' is specified.

Also, lndir will not create the 'todir', you have to create it first if it does not exist.

cmd:ln

Usage

file

ln -s index.htm index.html

dir

ln -s ~/ndl/libwww ~/install/libwww

— works fine for this case, but not for www well, it depends on how apache is configured. <<:2000.08.03 Thu:>>

link certain files to other dir

iitrc:~/ndl/libwww$ ls *me | xargs1 ln {} ~/www/tools/libwww

— has to do this way, for files out side of www, hard link *N*: use hard link IFF for www!

link certain files from other dir

ls ~+1/* | xargs -n 1 ln -s
ls ~+1/* | doeach ln -s @_


	'doeach.pl ln -s ./@_ ~+1/' doesn't work! ln just takes whatever from the command line and create the file as is. No hidden processing.

link a bunch of files from other dirs current one, relative

cd /opt/bin
ln -s ../pkg1/bin/* .

make same type of link across different dirs, relative

Obj: All sub dirs that contains file ++index.html,
    create a relative sym link to it named index.html

ff . ++index.html | sed 's|/++|/|'  | xargs1 ln -sf ++index.html

$ dir ./news/e21/usCommentary/2001/0329/index.html
 ./news/e21/usCommentary/2001/0329/index.html -> ++index.html


	file ++index.html need not exist in current dir!

link a bunch of files from one dir to another!, abs

ln -s /usr/local/teTeX/bin/sparc-solaris/* /usr/local/bin
ln -s /usr/local/teTeX/man/man1/* /usr/local/man/man1
ln -s /usr/local/teTeX/man/man5/* /usr/local/man/man5
ln -s /usr/local/teTeX/info/*info* /usr/local/info

link a bunch of files from one dir to another!, relative

ln -s some_dir/* .


	link from somewhere else to current dir:

/usr/shared# ln -s teTeX/bin/tie bin
/usr/shared# dir bin/tie
lrwxrwxrwx   1 root     other          13 Aug  3 18:12 bin/tie -> teTeX/bin/tie

— nono

/usr/shared/bin# ln -s ../teTeX/bin/tie .

/usr/shared/bin# dir tie
lrwxrwxrwx   1 root     other          16 Aug  3 18:14 tie -> ../teTeX/bin/tie*

/usr/shared/bin# ln -s ../teTeX/bin/* .

Test

1<<, >>

host:~/www>ln index.htm index.html
host:~/www>dir
-rw-r--r--   2 034897s cstudent      174 Feb 17 14:56 index.htm
-rw-r--r--   2 034897s cstudent      174 Feb 17 14:56 index.html

— two "same" files, with "link count" of 2

2<<, >>

host:~/www>ln -s index.htm index.html
ln: index.html: File exists
host:~/www>rm index.html
host:~/www>dir
-rw-r--r--   1 034897s cstudent      174 Feb 17 14:56 index.htm

— index.htm still remains after rm index.html, "link count" down to 1

3<<, >>

host:~/www>ln -s index.htm index.html
host:~/www>dir
-rw-r--r--   1 034897s cstudent      174 Feb 17 14:56 index.htm
lrwxrwxrwx   1 034897s cstudent        9 Feb 17 15:03 index.html -> index.htm

— two files, one is symbolic links, "link count" are still 1

4<<, >>

host:~/ndl>ln get-1.5.3.tar.gz ~/www/tools

host:~/ndl>dir ~/www/tools
total 463
-rw-r--r--   2 034897s cstudent   446966 Feb 17 20:53 get-1.5.3.tar.gz

*N*: can't do a symbolic link this time, web server refuse to get files out of www dir. For links from web to home file only, have to use hard links!

help

NAME

ln - make links between files

SYNOPSIS

ln [options] source [dest]
ln [options] source... directory

It  is  an error  if the last argument is not a directory and more than
two files are given.  It makes hard links  by  default.   By default, it
does not remove existing files.

-s, --symbolic
     Make symbolic links instead of hard links.  This option
     produces  an  error message on systems that do not sup-
     port symbolic links.