CODEWITHSUNDEEP
coperating-systemcommand-line-arguments
krupal
krupal

Reputation: 403

Argument treatment at command line in C

The question asked to me is that even if we supplied integer/float arguments at the command prompt they are still treated as strings or not in C language. I am not sure about that can any help just little bit. Is this true or not in C language and why? And what about others like Java or python ?

Upvotes: 1

Views: 448

Answers (3)

Elazar
Elazar

Reputation: 21645

Basically, this is an issue of creating an interface between the operating system and the program. any program. Remember that programs are not always written in C, And you don't even know whether there are things like float or int in the language.

You want to be able to pass several arguments (with natural delimiters), which may easily encode arbitrary information. In C, strings can be of arbitrary length, and the only constraint on them is that a zero byte in them signifies the end of the string. this is a highly flexible and natural way to pass arbitrary information to the program.

So you can never supply an arbitrary integer/float arguments directly to a program; The operating system (Unix / Linux / Windows / etc.) won't let you. You don't have any tool that gives you that interface, in the same way that you can't pass a mouse-click as an argument. All you supply is a sequence of characters.

Since Unix and C were designed together, it is also part of the C programming language, and from there it worked its way to C++, Java, Python and most other modern programming languages, and the same way into Linux, Windows and most other operating systems.

Upvotes: 0

user2513931
user2513931

Reputation:

It's not unlike mailing a letter without an envelope. We all agree to use the common enclosure known as an envelope. Operating systems pass parameters to programs using the common item known as a string of characters. It's beyond the scope of the operating system to understand what the program wants to do with the parameters.

There are some exceptions, one which comes to mind is the passing of parameters to a Linux Kernel Module. These can be passed as items other than strings.

Upvotes: 1

Jonathan Leffler
Jonathan Leffler

Reputation: 754860

It is true, independent of the language, that the command line arguments to programs on Unix are strings. If the program chooses to interpret them as numbers, that is fine, but it is because the program (or programmer) chose to do so. Similarly, the runtime support for a language might alter the arguments passed by the o/s into integer or float types, but the o/s passes strings to that runtime (I know of no language that does this, but I don't claim to know all languages).

To see this, note that the ways to execute a program are the exec*() family of functions, and each of those takes a string which is the name of the program to be executed, and an array of strings which are the arguments to be passed to the program. Functions such as system() and popen() are built atop the exec*() family of functions — they also use fork(), of course. Even the posix_spawn() function takes an array of pointers to strings for the arguments of the spawned program.

Upvotes: 2

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