{"id":5819,"date":"2023-04-08T00:01:33","date_gmt":"2023-04-08T07:01:33","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=5819"},"modified":"2023-03-25T11:24:13","modified_gmt":"2023-03-25T18:24:13","slug":"properly-padding-spaces-and-tabs","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=5819","title":{"rendered":"Properly Padding Spaces – and Tabs"},"content":{"rendered":"

As you can tell by the post title, part of the sconvert<\/em> program I missed is to convert tab characters into HTML spaces. Like spaces, tabs output blanks that must be converted to the &nbsp;<\/code> code for proper output on a web page.
\n
\nIn last week’s Lesson<\/a>, I told the riviting story of the sconvert<\/em> utility, which I use to process program output for this blog. It replaces spaces with the &nbsp;<\/code> (non-breakable space) HTML code. This program automates the conversion for me, so I don’t manually replace the spaces in sample output, which is a pain and takes time.<\/p>\n

The first draft of the code, however, didn’t convert tabs. Adding tab detection and output routines requires updating the existing code. To avoid messy if-else<\/em> decisions, I chose to use a switch-case<\/em> structure to evaluate and convert streaming input:<\/p>\n

2023_04_08-Lesson.c<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n    int ch;\r\n\r\n    while(1)\r\n    {\r\n        ch = getchar();\r\n        if( ch==EOF )\r\n            break;\r\n        switch(ch)\r\n        {\r\n            case ' ':\r\n                printf(\"&nbsp;\");\r\n                break;\r\n            case '\\t':\r\n                printf(\"&nbsp;&nbsp;&nbsp;&nbsp;\");\r\n                break;\r\n            default:\r\n                putchar(ch);\r\n        }\r\n    }\r\n\r\n    return(0);\r\n}<\/pre>\n
Immediately after grabbing a character from standard input, an if<\/em> test checks for the EOF<\/code>. When it floats in, the endless while<\/em> loop is broken.<\/p>\n
The switch-case<\/em> structure looks for twoitems: a space, or a tab. The default<\/em> condition is to output the character input, ch<\/code>. Otherwise, for the space or tab, one or four HTML non-breakable space codes (&nbsp;<\/code>) are output.<\/p>\n
This update to the code converts tabs into non-breakable spaces for HTML output. One thing the code doesn’t do is to calculate tab offsets.<\/p>\n
For example, I wrote a program that outputs the days of the week followed by a number value. Figure 1 shows the output as it appears on the screen:<\/p>\n
\"Screenshot\"
Figure 1. Text output with tabs may not line up perfectly. (Tab stops set every eight positions.)<\/p><\/div>\n
Yes, the program output is ugly because tab stops in the terminal are set every eight column positions. Here is how the updated sconvert<\/em> program interprets the output:<\/p>\n
Monday    0
\nTuesday    1
\nWednesday    2
\nThursday    3
\nFriday    4
\nSaturday    5
\nSunday    6<\/code><\/p>\n
Oops, the results are different. The program merely translates tabs into non-breakable HTML space codes without consideration for actual tab stops on the terminal. To more accurately convert tabs, more manipulation is required in the code, which I cover in next week’s Lesson.<\/p>\n","protected":false},"excerpt":{"rendered":"
The space character isn’t the only character that outputs blanks at the terminal. Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-5819","post","type-post","status-publish","format-standard","hentry","category-main"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5819","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5819"}],"version-history":[{"count":10,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5819\/revisions"}],"predecessor-version":[{"id":5836,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5819\/revisions\/5836"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5819"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5819"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5819"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}