Skip to main content

Use Carriage Return for Simple Progress Bar in Text Applications

Since most systems, including Unix, use LF(\n, 0x0A) as a newline character, using of CR(\r, 0x0D) is quite rare. One of the few cases where CR is used in modern computers is when creating progress bars in text applications. Using CR allows for a simple implementation of progress bars in terminals.

The code above draws a progress bar with # and ' '(space). For convenience, I fixed the progress bar's length at 20 characters, adding one # for every 5% increase in progress. When using CR to draw a progress bar like this, there are three points to consider.

The first point is to draw the progress bar on stderr instead of stdout. One of the significant differences between stdout and stderr is that stdout buffers output rather than immediately displaying it on the screen. Typically, stdout buffers output until it encounters a newline character. Therefore, if you print a progress bar without a newline character on stdout, the screen will not be updated until the progress bar is complete. If you need to use stdout for some reason, you must call the flush(stdout) function explicitly.

The second point is that the length of the string to be printed next should not be shorter than the previously printed string. CR only moves the cursor to the beginning of the line; it does not erase the current line. While this is not a concern for fixed-length progress bars, more complex control sequences may be needed to erase the current line or use space characters to erase the remaining characters when repeatedly outputting various strings on the same line.

The last point is not to output other strings while updating the progress bar. The code above assumes that only the progress bar will be drawn until it is complete. If other strings are printed in the middle, the result will differ entirely from what was intended.

Using control sequences allows for a perfect implementation that repeatedly modifies the same line, like the progress bar. However, using control sequences for simple programs like data processing can be overkill. Using CR alone can provide a simple and efficient implementation for displaying progress in simple programs.

Labels:

Comments

Post a Comment

Popular posts from this blog

[C++] Handling Exceptions in Constructors

When you use RAII idiom, there are often situations where constructors have to do complex tasks. These complex tasks can sometimes fail, resulting in throwing exceptions. This raises a concern: Is it okay to throw exceptions in constructors? The first concern is memory leaks. Fortunately, memory leaks do not occur. Variables created on the stack are released through stack unwinding, and if an exception occurs during heap allocation with the new operator, the new operator automatically deallocates the memory and returns nullptr . The next concern is whether the destructor of the member variables will be called correctly. However, this is also not a problem. When an exception occurs, member variables can be divided into three categories: fully initialized member variables, member variables being initialized, and uninitialized member variables. Fully initialized member variables have had their constructors called and memory allocations completed successfully. In the example code, t
Post a Comment
Read more

Iterator Adapters in Rust

An Iterator that takes another iterator and returns a new one is called an iterator adapter . The name "adapter" comes from one of the GoF's design patterns, the adapter pattern . However, in reality, it corresponds more to the decorator pattern , so if you pay too much attention to the name, you might get confused about its purpose. So it's better not to worry too much about the name. Enough complaining about the name, what does an iterator adapter do? An iterator adapter adds a task to be performed when the iterator iterates. This will be easier to understand when you see an example. The map function is one of the famous adapters. The iterator returned by the map function for those who have used functional languages iterates over new values transformed from the original values. Besides, various adapters are already implemented in the standard library. Among them, the most frequently used are those that are convenient to use with loops. Examples include the
Post a Comment
Read more

Difference Between the clear Command in Linux and Mac

I've been writing a series of posts about CSI Sequences, but we rarely use CSI Sequences directly. However, there is a CSI Sequence that we use unknowingly. It's the clear command that clears the screen. The clear command basically uses two types of CSI sequences. One is CSI H ( Cu rsor P osition, a.k.a CUP); it moves the cursor to the beginning of the screen. The cursor is at the top-left corner after the command ends, thanks to CUP. The second CSI Sequence is CSI 2 J ( E rase in D isplay, a.k.a. ED), which is used to clear the entire screen. Linux and Mac use these two sequences; they behave the same way up to this point. However, Linux's clear and Mac's differ in their subsequent actions. In a nutshell, Linux's clear clears the scrollback buffer, while Mac's does not. Linux's one prints CSI 3 J after the two sequences. CSI 3 J is an extension of the Escape Sequence introduced by xterm that removes lines stored in the scrollback buffer. Since be
Post a Comment
Read more