How can I clean up misaligned columns in text?

Question

I have a C program that outputs two columns, utterly misaligned. The reason for the misalignment is lengths of words in the first column are very different.

I have an o

Answer 1

Presumably you are using printf to output the columns in the first place. You can use extra modifiers in your format string to make sure things get aligned.

• To print a column of a specific width (right-justified), add the width before the formatting flag, e.g., "%10s" will print a column of width 10. If your string is longer than 10 characters, the column will be longer than you want, so choose a maximum value. If the string is shorter, it will be padded with spaces.
• To left-justify a column, put a - sign in front, e.g., "%-10s". I like to left-justify strings and right-justify numbers, personally.
• If you are printing addresses, you can change the fill characters from spaces to zeroes with a leading zero: "%010x".

To give a more in depth example:

printf("%-30s %8s %8s\n", "Name", "Address", "Size");
for (i = 0; i < length; ++i) {
    printf("%-30s %08x %8d\n", names[i], addresses[i], sizes[i]);

This would print three columns like this:

Name                            Address     Size
foo                            01234567      346
bar                            9abcdef0     1024
something-with-a-longer-name   0000abcd     2048