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

Type Conversion in Rust

Type conversion is not special in Rust. It's just a function that takes ownership of the value and returns the other type. So you can name convert functions anything. However, it's a convention to use as_ , to_ , and into_ prefixed name or to use from_ prefixed constructor. From You can create any function for type conversion. However, if you want to provide generic interfaces, you'd better implement the From trait. For instance, you should implement From<X> for Y when you want the interface that converts the X type value to the Y type value. The From trait have an associated function named from . You can call this function like From::from(x) . You also can call it like Y::from(x) if the compiler cannot infer the type of the destination type. Into From have an associated function, it makes you be able to specify the destination type. It's why From has an associated function instead of a method, but on the other hands, you cannot use it as a me
Post a Comment
Read more

Do not use garbage collection to catch memory leak

Garbage collection is a technique that automatically releases unnecessary memory. It's very famous because many programming languages adopted garbage collection after John McCarthy implemented it in Lisp. However, there are a few people who misunderstand what garbage collection does. If you think garbage collection prevents a memory leak, unfortunately, you are one of them. Garbage collection cannot prevent a memory leak. There is no way to avoid all memory leaks if you are using Turing-complete language. To understand it you should know what a memory leak is. Wikipedia describes a memory leak as the following: a type of resource leak that occurs when a computer program incorrectly manages memory allocations in such a way that memory which is no longer needed is not released. Briefly, a memory leak is a bug that doesn't release a memory that you don't use. So it is first to find the memory which will not be used in order to detect memory leaks. Unfortunately, it i
Post a Comment
Read more

[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