Thread: writing a grep program

Hi,
This is not a homework problem. This is a sample test problem and I wanted to know how to do it. It would be great if someone can help me. The question is:

Write a program, similar to grep, using regcomp(3C) and regexec(3C) to search for a regular expression pattern in standard input. Program synopsis:

./p1 pattern

Simple search for regular expression pattern in standard input.

Exit status:

0 One or more matches were found
1 No matches were found
2 Syntax errors or inaccessible files (even if matches were found)

Use regcomp flags: REG_NEWLINE | REG_NOSUB
Use a function in the form:

void regex_search( regex_t *preg, FILE *fp)

to perform the search. This function will be invoked from the main program as:
regex_t reg;
...
regex_search( &reg, stdin);


I did not undertsnd how to do it as I am not very familiar with C. I am from an IC design background. It would be a great help for my exam preparations, if somebody can help me with this.

Thankyou very much.
-Cnovice

Use fgets() to read each line from a file.
Apply your regex matcher to each line.

Lather, rinse and repeat until end of file.

fgets() is part of the c++ language isn't it?

and printf() is also part of the c++ language, although admittedly not commonly used in c++ programs

> I did not undertsnd how to do it as I am not very familiar with C.
I didn't read the board, I read this.
Hence the 'C' answer.

Moved to the 'C' board.

Originally Posted by dwks

Okay, then, it's like using malloc(). Yeah, you can use it, but there are alternatives. (new, in the case of malloc.)

(You're not supposed to use malloc() in C++ programs because it just allocates memory, it doesn't call constructors.)

but sometimes that's all you want anyway, especially when allocating arrays of PODs or structures that contain nothing but POD data objects. However, for consistency, I agree with you that malloc() and new should not be used in the same breath (program).