Formatting Output Strings with Right Alignment in C

When processing text files containing data, such as coordinates, the need to align items in columns for proper formatting often arises. In C , the manipulation of output strings is crucial to achieve this alignment. This article addresses the issue of right-aligning output strings, providing solutions using standard C techniques.

To process the input text file, the line.split() function is employed to delimit each line into its x, y, and z coordinates. After processing, the goal is to write the coordinates back to a txt file with right alignment to match the input file's format.

Initially, the new line is constructed using string concatenation:

line_new = words[0]    '  '   words[1]    '  '   words[2];

However, this approach does not provide the desired alignment. To achieve this alignment, we can use string formatting techniques.

Using C String Formatting

C offers several ways to format strings, including the modern str.format syntax and the older printf-style formatting.

Using str.format

The str.format syntax allows for flexible string formatting, enabling easy alignment and field width specification. To right-align each coordinate, the following syntax can be used:

line_new = '{:>12}  {:>12}  {:>12}'.format(word[0], word[1], word[2]);

This syntax specifies that each coordinate should be right-aligned with a field width of 12 characters.

Using printf-Style Formatting

For older versions of C that do not support str.format, printf-style formatting can be used. This approach is less flexible but still allows for field width specification:

line_new = 's  s  s' % (word[0], word[1], word[2]);

This syntax also specifies a field width of 12 characters for each coordinate.

By utilizing these string formatting techniques, it becomes straightforward to right-align coordinates when writing to txt files.