emv@math.lsa.umich.edu (Edward Vielmetti) (09/24/90)
In article <4002@umbc3.UMBC.EDU> rouben@math9.math.umbc.edu writes:
How can I count the number of occurrences of a given character in a file?
It can be done rather trivially in C, but I wonder if it can also be done
using standard unix utilities like awk, sed, tr, wc, etc.
The closest I have come to this is the following construction:
cat file | tr -c 'A' '' | wc -c
This is what I came up with in perl, after about 15 minutes of digging
in the perl info pages:
cat file | perl -ne '$c += tr/A/A/; if (eof()) {print "$c\n";}'
Going back to the tr man page this one seems to work too:
cat file | tr -cd 'A' | wc -c
I don't see an easy perl equivalent of the "tr -cd" idiom.
--Ed
Edward Vielmetti, U of Michigan math dept <emv@math.lsa.umich.edu>
moderator, comp.archivesmerlyn@iwarp.intel.com (Randal Schwartz) (09/24/90)
In article <EMV.90Sep23181658@picasso.math.lsa.umich.edu>, emv@math (Edward Vielmetti) writes: | Going back to the tr man page this one seems to work too: | | cat file | tr -cd 'A' | wc -c | | I don't see an easy perl equivalent of the "tr -cd" idiom. You *will* in Perl 4.0 (coming real soon). Perl is being upgraded with a few new features so that it matches the new specification ("The Book"). The 'tr' operator gets a few new options, namely 'c', 'd', and 's', acting just like their tr(1) cousins. By the way, you don't need all those 'cat file' things. Just go: perl -ne '$c += tr/A/A/; print $c if eof;' file One process fits all. print "Just another Perl [book] hacker," -- /=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\ | on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III | | merlyn@iwarp.intel.com ...!any-MX-mailer-like-uunet!iwarp.intel.com!merlyn | \=Cute Quote: "Welcome to Portland, Oregon, home of the California Raisins!"=/
ted@nmsu.edu (Ted Dunning) (09/24/90)
i didn't want to answer this one, but In article <EMV.90Sep23181658@picasso.math.lsa.umich.edu> emv@math.lsa.umich.edu (Edward Vielmetti) writes: In article <4002@umbc3.UMBC.EDU> rouben@math9.math.umbc.edu writes: ... cat file | tr -c 'A' '' | wc -c ... ... cat file | tr -cd 'A' | wc -c ed must have been kidding when he left the cat in place, instead of tr -cd 'A' < file | wc -c -- ted@nmsu.edu +---------+ | In this | | style | |__10/6___|
aks@hub.ucsb.edu (Alan Stebbens) (09/25/90)
In article <4002@umbc3.UMBC.EDU> rouben@math9.math.umbc.edu writes:
rouben> How can I count the number of occurrences of a given character
rouben> in a file? It can be done rather trivially in C, but I wonder
rouben> if it can also be done using standard unix utilities like awk,
rouben> sed, tr, wc, etc.
rouben> The closest I have come to this is the following construction:
rouben> cat file | tr -c 'A' '' | wc -c
ed> Going back to the tr man page this one seems to work too:
ed> cat file | tr -cd 'A' | wc -c
ed> I don't see an easy perl equivalent of the "tr -cd" idiom.
Try:
perl -ne '$s+=tr/A//;if(eof){print $s,"\n";}' fileworley@compass.com (Dale Worley) (09/25/90)
X-Name: Randal Schwartz perl -ne '$c += tr/A/A/; print $c if eof;' file Doesn't this fail if the file is empty? Dale Worley Compass, Inc. worley@compass.com -- Using MS-DOS on a '386 is like using a Formula 1 race car to do your grocery shopping.
merlyn@iwarp.intel.com (Randal Schwartz) (09/26/90)
In article <1990Sep25.151014.11935@uvaarpa.Virginia.EDU>, worley@compass (Dale Worley) writes: | | X-Name: Randal Schwartz | | perl -ne '$c += tr/A/A/; print $c if eof;' file | | Doesn't this fail if the file is empty? Ooops. I'll be out painting fence-posts for a while, sorry. :-) -- /=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\ | on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III | | merlyn@iwarp.intel.com ...!any-MX-mailer-like-uunet!iwarp.intel.com!merlyn | \=Cute Quote: "Welcome to Portland, Oregon, home of the California Raisins!"=/
worley@compass.com (Dale Worley) (09/26/90)
From: merlyn@iwarp.intel.com (Randal Schwartz) | perl -ne '$c += tr/A/A/; print $c if eof;' file | | Doesn't this fail if the file is empty? Ooops. I'll be out painting fence-posts for a while, sorry. :-) It seems like it would be useful to be able to prescribe prolog and epilog code for -n (and -p) loops. AWK does this with BEGIN and END. Then it would be simple: perl -ne '$c += tr/A/A/' -xxx 'print $c' file Dale Worley Compass, Inc. worley@compass.com -- Give yourself over to absolute pleasure Swim the warm waters of sins of the flesh Erotic madness beyond any measure And sensual daydreams to treasure... forever. -- Rocky Horror Picture Show
lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) (09/27/90)
In article <1990Sep26.125033.19669@uvaarpa.Virginia.EDU> worley@compass.com writes:
:
: From: merlyn@iwarp.intel.com (Randal Schwartz)
:
: | perl -ne '$c += tr/A/A/; print $c if eof;' file
: |
: | Doesn't this fail if the file is empty?
:
: Ooops. I'll be out painting fence-posts for a while, sorry. :-)
:
: It seems like it would be useful to be able to prescribe prolog and
: epilog code for -n (and -p) loops. AWK does this with BEGIN and END.
: Then it would be simple:
:
: perl -ne '$c += tr/A/A/' -xxx 'print $c' file
It hardly seems worth it to add a new switch when you can say
perl -e 'while(<>){$c += tr/A/A/;}print $c' file
or
perl -ne '$c += tr/A/A/; print $c if eof()' file
or
perl -e 'undef $/; $_ = <>; print tr/A/A/' file
or even
perl -e '$c += tr/A/A/ while <>; print $c' file
Although the Perl Slogan is There's More Than One Way to Do It, I hesitate
to make 10 ways to do something. :-)
Larry