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This article introduces the relevant knowledge of "how to use GNU bc to perform mathematical operations in Linux Shell". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Use bc to do arithmetic better in shell, which is a mathematical language for advanced computing.

Most POSIX systems come with GNU bc, a digital processing language with arbitrary precision. Its syntax is similar to C, but it also supports interactive execution of statements and processing of data from standard input (stdin). Therefore, it is usually the answer to the following question: "how do I do math in Linux shell?" This kind of response is common on the Internet:

$echo "1mm 1" | bc2

Although this is absolutely true, few users think it is elegant compared to a more intuitive way, such as:

$1 million 1 # this doesn't work 2

The interaction mode is easier:

$bc1+12quit$

But the interactive mode is not always suitable for the intuitive workflow that simple calculations want, such as directly entering the calculations you want. So I recommend Bluebat's pure Bash calculator.

Bc actually provides a mathematical language for advanced computing.

Mathlib with advanced functions

Bc itself provides basic mathematical functions. You can test them in interactive mode:

$bc3 ^ 29 (3 ^ 2) * (9) / 327

Use the-- mathlib option to get advanced functions, including sine, cosine, tangent, and so on. In interactive mode, you can test some of them. Here is the cosine of 90 degrees:

C (90)-.44807361612917015236

The sine of 9:

S (9) .41211848524175656975 create your own bc function

You can also create your own functions in bc. The function definition starts with the define keyword and is enclosed in curly braces. Here is a simple function entered into an interactive session that returns any number it has:

$bcdefine echo (n) {return (n);}

In the same interactive session, test:

If statement in echo (2) 2echo (- 2)-2bc

The bc language also has a variety of control statements, the simplest of which is if/else. The syntax may seem familiar at first glance, but there are some differences in how to deal with curly braces. Note that the else clause of the if statement is enclosed in curly braces, while the then clause is not, but both are terminated with semicolons. Here is a function that returns the absolute value of the number n:

Define abso (n) {if (n > 0) return (n); {return (- n);}}

In the same interactive session, test:

Abso (- 5) 5abso (5) 5 imports data into bc

The use of interactive sessions is tolerated for fast calculations and experiments, but data is lost on exit and is difficult to edit when something goes wrong. Fortunately, bc can load variables and functions from external files.

Here is a file containing two variables (sol and foo), as well as a custom abso function for finding absolute values:

Sol=299792458 foo=42 define abso (n) {if (n > 0) return (n); {return (- n);}}

Save it to a file named bcvars.bc to import the bc interactive session:

$bc bcvars.bcfoo42sol299792458abso (- 23) 23 use bc to help you with your math

The bc language is relatively simple, as long as you know enough mathematics to construct any equation you want. Although bc provides useful basic functions by default and allows you to create your own functions, you can reduce your workload by standing on the shoulders of giants. Files loaded with new functions for mathematical fundamentals and specific tasks (for example, calculating compound interest) are available from the GNU bc page, as well as complete bc documentation.

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