A filter is a program that accepts standard input and generates standard output. These programs are fun to write, providing you have a goal in mind and some way to manipulate the incoming text in a manner that’s significant enough to notice in the output.
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\nFor the past five years on this blog, I’ve written several posts on filters:<\/p>\n
Lesson – The Caesarian Cipher<\/a> It’s time for another!<\/p>\n This idea came to me while I was working on another programming project. I needed to generate text in Title Case, which is also known as Initial Caps. The goal is to capitalize the first letter of each word. I figured it’s a good task for a filter.<\/p>\n For a filter, all input comes from standard input, or the stdin<\/em>, device. All output is sent to standard output, the stdout<\/em> device. Both stdin<\/em> and stdout<\/em> are defined in C, which means you can use standard I\/O or file I\/O functions to fetch and put characters.<\/p>\n The following code presents a simple I\/O filter that doesn’t modify input:<\/p>\n The while<\/em> loop between Lines 7 and 13 is an infinite loop, which is typical for a filter. The getc()<\/em> function at Line 9 fetches a character from standard input, At Line 10, the Line 12 outputs the same character. In a true filter, like the one you are challenged to create for this Exercise, more action must happen between the if<\/em> test and putchar()<\/em>.<\/p>\n Using the skeleton provided above (or you can create your own), process input so that the first letter of a word is capitalized and the rest of the characters in the word appear as lower case.<\/p>\n Here are some sample runs to demonstrate what the filter does:<\/p>\n The odd-numbered lines (1, 3, and 5) appear as typed. After Enter is pressed, the filter spits out the modified line (lines 2, 4, and 6).<\/p>\n Your task is to write such a filter. It might be trickier than you think, but it can be done! Click here<\/a> to view my solution, though please try this Exercise on your own before you see how I’ve solved it.<\/p>\n","protected":false},"excerpt":{"rendered":" Gently massage text so that Each Word Is Capitalized. Continue reading
\nLesson – One Word at a Time<\/a>
\nSeries – Encoding and Decoding<\/a>
\nLesson – Safe Coding Practices getchar()<\/em> and putchar()<\/em><\/a>
\nLesson – A Word Wrap Filter (Part 1 of 2)<\/a>
\nExercise – The URL Encoding Filter<\/a>
\nExercise – The URL Decoding Filter<\/a><\/p>\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 = getc(stdin);\r\n if( ch == EOF)\r\n break;\r\n putc(ch,stdout);\r\n }\r\n\r\n return(0);\r\n}<\/pre>\nstdin<\/code>.<\/p>\nEOF<\/code> (End of File) condition is checked for. If found, the loop is broken and the program stops. EOF<\/code> is an integer constant, which is why variable ch<\/code> is defined as an int<\/em>, not a char<\/em>.<\/p>\nthis is all lower case
\nThis Is All Lower Case
\nTHIS IS ALL CAPS
\nThis Is All Caps
\nThis Is Already Initial Caps
\nThis Is Already Initial Caps<\/code><\/p>\n