{"id":7369,"date":"2004-03-23T02:15:40","date_gmt":"2004-03-23T00:15:40","guid":{"rendered":"https:\/\/mamchenkov.net\/wordpress\/2004\/03\/23\/calculator-at-hand\/"},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-29T22:00:00","slug":"calculator-at-hand","status":"publish","type":"post","link":"https:\/\/mamchenkov.net\/wordpress\/2004\/03\/23\/calculator-at-hand\/","title":{"rendered":"Calculator at hand"},"content":{"rendered":"\n

\t\"\"UNIX shell is excellent. The toolbox at hand also never stop to amaze. But sometimes there is this feeling that something is missing. No matter how many tools are there, you’ll still want something special and personalized.<\/p>\n

I am pretty often missing the calculator. Of course, there are xcalc and kcalc for graphical interface, but that’s just too slow for something that I should actually do in my head. There is bc(1) for console, but I never liked it for quick stuff. expr(1) is pretty close, but it needs a rather complex syntax like “expr 1 ‘+’ 2”.\n<\/p>\n

\t<\/p>\n

So here I am with a need for simple console calculator. Here is what I do – write a small perl script:<\/p>\n


\n
\n#!\/usr\/bin\/perl -w<\/p>\n

use strict;<\/p>\n

my $expr = shift;
\n
\nmy $verbose = $expr eq '-v' ? 1 : 0;<\/p>\n

$expr = shift if ($verbose);
\n
\ndo {
\n
\n my $result = eval($expr);
\n
\n print $expr . ' = ' if ($verbose);
\n
\n print eval($expr) . \"
\n\";
\n
\n} while ( $expr = shift);
\n
\n<\/code><\/p>\n<\/div>\n

This can be than placed into any directory in the path and used as following:<\/p>\n


\n
\n[leonid@home tmp]$ calc.pl \"2+3\"
\n
\n5
\n
\n<\/code><\/p>\n<\/div>\n

The beauty of it is that it can do several equations at once and not only equations:<\/p>\n


\n
\n[leonid@home tmp]$ KOEF=`calc.pl '10 + 5'`
\n
\n[leonid@home tmp]$ calc.pl -v \"$KOEF * 2\" \"sqrt(256)\" \"localtime(time)\"
\n
\n15 * 2 = 30
\n
\nsqrt(256) = 16
\n
\nlocaltime(time) = Thu Feb 26 04:28:25 2004
\n
\n<\/code><\/p>\n<\/div>\n

This ‘-v’ option causes calc.pl to print out the equation as well. Now I can totally forget arithmetics. :)<\/p>\n\n","protected":false},"excerpt":{"rendered":"\n

UNIX shell is excellent. The toolbox at hand also never stop to amaze. But sometimes there is this feeling that something is missing. No matter how many tools are there, you’ll still want something special and personalized. I am pretty often missing the calculator. Of course, there are xcalc and kcalc for graphical interface, but … Continue reading Calculator at hand<\/span><\/a><\/p>\n\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_links_to":"","_links_to_target":""},"categories":[1,62],"tags":[],"keyring_services":[],"class_list":["post-7369","post","type-post","status-publish","format-standard","hentry","category-general","category-technology"],"aioseo_notices":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack-related-posts":[{"id":26722,"url":"https:\/\/mamchenkov.net\/wordpress\/2016\/10\/11\/the-curious-case-of-the-switch-statement\/","url_meta":{"origin":7369,"position":0},"title":"The curious case of the switch statement","author":"Leonid Mamchenkov","date":"October 11, 2016","format":false,"excerpt":"\"The curious case of the switch statement\"\u00a0is a nice historical perspective on the switch statement in most modern programming languages, where it come from, and how it transformed over the years. \u00a0It starts of with ALGOL 58 (yes, a programming language from 1958), and traces the history down to the\u2026","rel":"","context":"In "All"","block_context":{"text":"All","link":"https:\/\/mamchenkov.net\/wordpress\/category\/general\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":10682,"url":"https:\/\/mamchenkov.net\/wordpress\/2007\/03\/23\/sms-alerts-for-new-email-via-twitter\/","url_meta":{"origin":7369,"position":1},"title":"SMS alerts for new email via Twitter","author":"Leonid Mamchenkov","date":"March 23, 2007","format":false,"excerpt":"As I have mentioned previously, Twitter has many uses. 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