Extract a substring of n digits from a string
in [Shell]
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From: Dan Mercer on 28 Oct 2005 20:12 "William Park" <opengeometry(a)yahoo.ca> wrote in message news:5202b$43617e07$d8fea14c$3893(a)PRIMUS.CA... : Dan Mercer <dmercer(a)mn.rr.com> wrote: : > "William Park" <opengeometry(a)yahoo.ca> wrote in message news:f2abd$43603ea4$d8fe9d17$6594(a)PRIMUS.CA... : > : Giacomo <a(a)b.cde> wrote: : > : > asdasd 123 asd 191991 1234 : > : > lijoioi 4567 asdi 67567 iojoii : > : > : > : > For n=4 the result for each line must be 1234 e 4567. : > : : > : a='asdasd 123 asd 191991 1234 lijoioi 4567 asdi 67567 iojoii' : > : RE='\<[0-9]{4}\>' : > : echo "${a|+$RE}" : > : > This can be down in the shell. Assuming lines containing only lower case letters and : > numbers: : > : > ifs=$IFS : > IFS="${IFS}abcdefghijklmnopqrstuvwxyz" : > while read line : > do : > IFS=$ifs : > set -- $line : > IFS=$ifs : > set -- $* : > for i : > do : > ((${#i} == 4)) && echo "$i" : > done : > done : > : > Now, this isn't the efficient way to do it. That would probably be : > best done in perl. : : Interesting approach. I would probably do it as : for i in `tr -c '0-9' ' ' < file`; do : [ ${#i} -eq 4 ] && echo $i : done : or if there is lots of repetition, : func() : { : [ ${#1} -eq 4 ] : } : set -- `tr -c '0-9' ' ' < file` : echo ${@|?func} But the challenge is NOT to invoke external programs (;-) Dan Mercer : : -- : William Park <opengeometry(a)yahoo.ca>, Toronto, Canada : ThinFlash: Linux thin-client on USB key (flash) drive : http://home.eol.ca/~parkw/thinflash.html : BashDiff: Super Bash shell : http://freshmeat.net/projects/bashdiff/ |