Thread: compiler error

Hi all. Here's some partial code. I would love to post the whole code, but I am tired of spending 10 or more minutes after making a post
trying to format the text to fit the forum screen.

(Sorry, I've already spent 15 minute so far just editing this post), trying to stop the lines from running off the right edge of the screen. I give up.

If I have this:

Code:

struct data {
        int month, day, year, hour, minute;
        char string1[2+1];
        int number1, number2;
        char string2[FILENAMELENGTH];
        char stringstorage[LINELENGTH];		// Used to store strings from file
		char string3[FILENAMELENGTH];	// filenames that contain the search string
    } LineData[NUMBEROFFILES];

for( counter1 = BEGINNINGOFHTMLLIST; counter1 < (lastfilenumber - 1); counter1++) 
	{	
		if((p_openfile = fopen(LineData[counter1].string2, "rt")) == NULL)
		{
			perror("\nError opening file");
			exit(EXIT_FAILURE);
		}

		p_line = malloc(FILELINELENGTH * sizeof(char));

		while((fgets(p_line, FILELINELENGTH, p_openfile) != NULL))
		{
		counter2 = 0;
		if((p_searchstring = strstr(p_line,p_searchtext)) != NULL)
			{
				LineData[counter2].string3 = LineData[counter1].string2;  <=== compiler error(line 95)===
				break;
			}

			counter2++;
			free(p_line);
			p_line = malloc(FILELINELENGTH * sizeof(char));
			fclose(p_openfile);
		}
	}

I get the following compiler error:

Code:

(95) : error C2106: '=' : left operand must be l-value

I can't see what's wrong with it, and I don't understand VC++ 2008's explanation of what an l-value is:

Code:

Expressions that refer to memory locations are called "l-value" expressions. An l-value represents a storage
region's "locator" value, or a "left" value, implying that it can appear on the left of the equal sign (=). 
L-values are often identifiers. Expressions referring to modifiable locations are called "modifiable l-values." 
A modifiable l-value cannot have an array type, an incomplete type, or a type with the const attribute. 
For structures and unions to be modifiable l-values, they must not have any members with the const attribute. 
The name of the identifier denotes a storage location, while the value of the variable is the value
 stored at that location. 

An identifier is a modifiable l-value if it refers to a memory location and if its type is arithmetic, structure, union, or pointer. For example, if ptr is a pointer to a storage region, then *ptr is a modifiable l-value that designates the storage region to which ptr points. 

Any of the following C expressions can be l-value expressions: 

An identifier of integral, floating, pointer, structure, or union type 

A subscript ([ ]) expression that does not evaluate to an array 

A member-selection expression (–> or .) 

A unary-indirection (*) expression that does not refer to an array 

An l-value expression in parentheses 

A const object (a nonmodifiable l-value) 

The term "r-value" is sometimes used to describe the value of an expression and to distinguish it from an l-value. All l-values are r-values but not all r-values are l-values. 

Microsoft Specific 

Microsoft C includes an extension to the ANSI C standard that allows casts of l-values to be used as l-values, as long as the size of the object is not lengthened through the cast. (See Type-Cast Conversions for more information.) The following example illustrates this feature: 

  Copy Code 
char *p ;
short  i;
long l;

(long *) p = &l ;       /* Legal cast   */
(long) i = l ;          /* Illegal cast */
 

The default for Microsoft C is that the Microsoft extensions are enabled. Use the /Za compiler option to disable these extensions.

Thanks in advance for any and all help.

Bugger that, here's the entire code, if it is of any use to anyone.

Code:

#define _CRT_SECURE_NO_WARNINGS // To turn off VC++ 2008 deprecation warnings

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define NUMBEROFFILES 1500		// maximum number of files in the directory listing
#define LINELENGTH 150			// length of a line in the directory listing
#define FILENAMELENGTH 40		// length of an .html file
#define BEGINNINGOFHTMLLIST 5	// first html file in directory list
#define FILELINELENGTH 1000		// lengh of a line in an html file

int main( void )
{ 
    int lastfilenumber;
    FILE *p_openfile;
	char *p_comma;				// used to test for occurence of a comma in a line of the directory listing
	char *p_line;				// stores successive lines from a file from the directory listing
    int  counter1, counter2;
	char *p_searchstring; 
	char *p_searchtext = "every";		// string to search for in a file

	struct data {
        int month, day, year, hour, minute;
        char string1[2+1];
		int number1, number2;
        char string2[FILENAMELENGTH];
        char stringstorage[LINELENGTH];		// Used to store strings from file
		char string3[FILENAMELENGTH];		// filenames that contain the search string
    } LineData[NUMBEROFFILES];

    // Get a list of files in the directory "testwebsite", and redirect the
    // output to a file called "directorylisting.txt". */

	system("dir c:\\testwebsite\\*.html > directorylisting.txt");

    // Test to see that the file "directorylisting.txt" can be opened for reading.

    if( (p_openfile = fopen("directorylisting.txt", "rt")) == NULL)
    {
        perror("directorylisting.txt");
        exit( EXIT_FAILURE );
    }

    // Copy the lines in the file to the array 

    counter1 = 0;

    while((fgets(LineData[counter1].stringstorage, LINELENGTH, p_openfile) != NULL) && (counter1 < NUMBEROFFILES))
    {
		lastfilenumber = counter1;
        counter1++;	
    }

    fclose(p_openfile);

	// Process the string, and store data items in the structure members

	for( counter1 = BEGINNINGOFHTMLLIST; counter1 < lastfilenumber; counter1++)
	{
		if( (p_comma = strchr( LineData[counter1].stringstorage, ',')) != NULL )
		{
			sscanf(LineData[counter1].stringstorage, "%d%/%d/%d %d:%d %s %d,%d %s", &LineData[counter1].month,
                           &LineData[counter1].day, &LineData[counter1].year, &LineData[counter1].hour,
						   &LineData[counter1].minute, LineData[counter1].string1, &LineData[counter1].number1,							&LineData[counter1].number2, &LineData[counter1].string2);
		}

		if( (p_comma = strchr( LineData[counter1].stringstorage, ',')) == NULL )
		{
			sscanf(LineData[counter1].stringstorage, "%d%/%d/%d %d:%d %s %d %s", &LineData[counter1].month,
                        &LineData[counter1].day, &LineData[counter1].year, &LineData[counter1].hour,
						&LineData[counter1].minute, LineData[counter1].string1, &LineData[counter1].number1, 
						&LineData[counter1].string2);
		}
	}

	// open up a file, search for p_searchtext, if it exists, store filename(LineData[counter1].string2) in
	// LineData[counter2].string3

	for( counter1 = BEGINNINGOFHTMLLIST; counter1 < (lastfilenumber - 1); counter1++) 
	{	
		if((p_openfile = fopen(LineData[counter1].string2, "rt")) == NULL)
		{
			perror("\nError opening file");
			exit(EXIT_FAILURE);
		}

		p_line = malloc(FILELINELENGTH * sizeof(char));

		while((fgets(p_line, FILELINELENGTH, p_openfile) != NULL))
		{
			counter2 = 0;
			if((p_searchstring = strstr(p_line,p_searchtext)) != NULL)
			{
				LineData[counter2].string3 = LineData[counter1].string2;  
				break;
			}

			counter2++;
			free(p_line);
			p_line = malloc(FILELINELENGTH * sizeof(char));
			fclose(p_openfile);
		}
	}

    return 0;
}

EDIT: What I am trying to do with that while loop is to use fgets to put a string in a file into a pointer. Then search for another string within the first string. Then if the string is found in that file, copy the filename to LineData[counter2].string3(a member of the structure).

You cannot assign to an array in C.
You will have to manually copy every element over or use memcpy.
Oh and instead of putting code tags around explanations, use [quote][/quote] tags.