Thread: how to get data from a file in c

Use fgets() to read one line at a time and then, for each line, use sscanf() [Note the two s's] to parse the line and obtain/extract the values needed. Based on those values, calculate the mean.

Code:

char* third_column(char* str)
{
    char* ret = NULL;
    int space = 0;
    while( *str ) {
        space += *str == ' ';
        switch( space ) {
            case 2:
                if( *str == ',' ) { *str = '.'; }
                if( !ret ) { ret = str; }
            break;
            case 3:
                *str = '\0';
                return ret;
            break;
        }
        ++str;
    }
    return ret;
}

zub: I understand that you may find it easier to post code than to suggest a solution in English (or pseudocode), but it is poor form to post complete code for a significant function that could well be used as-is before the help seeker has shown an attempt. That said, I think your interpretation of the third column is (deliberately?) wrong, but it is still spoonfeeding. Please do not do this again.

Originally Posted by laserlight

That said, I think your interpretation of the third column is (deliberately?) wrong, but it is still spoonfeeding.

Code:

#include "greatest.h"

char* third_column(char* str)
{
    char* ret = NULL;
    int space = 0;
    while( *str ) {
        space += *str == ' ';
        switch( space ) {
            case 2:
                if( *str == ',' ) { *str = '.'; }
                if( !ret ) { ret = str; }
            break;
            case 3:
                *str = '\0';
                return ret;
            break;
        }
        ++str;
    }
    return ret;
}


TEST third_column_1()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.10.00 -2,0 G")), -2.0);
    PASS();
}


TEST third_column_2()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.20.00 -2,0 G")), -2.0);
    PASS();
}


TEST third_column_3()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.30.00 -2,1 G")), -2.1);
    PASS();
}


TEST third_column_4()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.40.00 -2,0 G")), -2.0);
    PASS();
}


TEST third_column_5()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.50.00 -2,3 G")), -2.3);
    PASS();
}


TEST third_column_6()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.00.00 -2,4 G")), -2.4);
    PASS();
}


TEST third_column_7()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.10.00 -2,1 G")), -2.1);
    PASS();
}


TEST third_column_8()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.20.00 -1,9 G")), -1.9);
    PASS();
}


TEST third_column_9()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.30.00 -2,1 G")), -2.1);
    PASS();
}


TEST third_column_10()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.40.00 -2,2 G")), -2.2);
    PASS();
}


TEST third_column_11()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.50.00 -2,1 G")), -2.1);
    PASS();
}


TEST third_column_12()
{
    ASSERT_EQ(atof(third_column("02/01/2007 03.00.00 -2,1 G")), -2.1);
    PASS();
}


SUITE(test_third_column)
{
    RUN_TEST(third_column_1);
    RUN_TEST(third_column_2);
    RUN_TEST(third_column_3);
    RUN_TEST(third_column_4);
    RUN_TEST(third_column_5);
    RUN_TEST(third_column_6);
    RUN_TEST(third_column_7);
    RUN_TEST(third_column_8);
    RUN_TEST(third_column_9);
    RUN_TEST(third_column_10);
    RUN_TEST(third_column_11);
    RUN_TEST(third_column_12);
}


GREATEST_MAIN_DEFS();


int main(int argc, char **argv) {
    GREATEST_MAIN_BEGIN();      /* command-line arguments, initialization. */
    RUN_SUITE(test_third_column);
    GREATEST_MAIN_END();        /* display results */
}

C:\UTIL\tcc>tcc.exe -run -Wall run.c


* Suite test_third_column:
............
12 tests - 12 pass, 0 fail, 0 skipped (4 ticks, 0.004 sec)


Total: 12 tests (9 ticks, 0.009 sec)
Pass: 12, fail: 0, skip: 0.

Originally Posted by whiteflags

When he said your interpretation is wrong, he didn't mean that the code is broken. In particular, I think he means you are assuming it is ok to change a datum like "2,0" into "2.0".

Indeed. zub, compile and run:

Code:

#include "greatest.h"
 
char* third_column(char* str)
{
    char* ret = NULL;
    int space = 0;
    while( *str ) {
        space += *str == ' ';
        switch( space ) {
            case 2:
                if( *str == ',' ) { *str = '.'; }
                if( !ret ) { ret = str; }
            break;
            case 3:
                *str = '\0';
                return ret;
            break;
        }
        ++str;
    }
    return ret;
}

TEST third_column_1()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.10.00 -2,0 G")), -1.0);
    PASS();
}
 
 
TEST third_column_2()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.20.00 -2,0 G")), -1.0);
    PASS();
}
 
 
TEST third_column_3()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.30.00 -2,1 G")), -0.5);
    PASS();
}
 
 
TEST third_column_4()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.40.00 -2,0 G")), -1.0);
    PASS();
}
 
 
TEST third_column_5()
{
    ASSERT_EQ(atof(third_column("02/01/2007 01.50.00 -2,3 G")), -0.5);
    PASS();
}
 
 
TEST third_column_6()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.00.00 -2,4 G")), 1.0);
    PASS();
}
 
 
TEST third_column_7()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.10.00 -2,1 G")), -0.5);
    PASS();
}
 
 
TEST third_column_8()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.20.00 -1,9 G")), 4.0);
    PASS();
}
 
 
TEST third_column_9()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.30.00 -2,1 G")), -0.5);
    PASS();
}
 
 
TEST third_column_10()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.40.00 -2,2 G")), 0.0);
    PASS();
}
 
 
TEST third_column_11()
{
    ASSERT_EQ(atof(third_column("02/01/2007 02.50.00 -2,1 G")), -0.5);
    PASS();
}
 
 
TEST third_column_12()
{
    ASSERT_EQ(atof(third_column("02/01/2007 03.00.00 -2,1 G")), -0.5);
    PASS();
}

SUITE(test_third_column)
{
    RUN_TEST(third_column_1);
    RUN_TEST(third_column_2);
    RUN_TEST(third_column_3);
    RUN_TEST(third_column_4);
    RUN_TEST(third_column_5);
    RUN_TEST(third_column_6);
    RUN_TEST(third_column_7);
    RUN_TEST(third_column_8);
    RUN_TEST(third_column_9);
    RUN_TEST(third_column_10);
    RUN_TEST(third_column_11);
    RUN_TEST(third_column_12);
}
 
 
GREATEST_MAIN_DEFS();
 
 
int main(int argc, char **argv) {
    GREATEST_MAIN_BEGIN();      /* command-line arguments, initialization. */
    RUN_SUITE(test_third_column);
    GREATEST_MAIN_END();        /* display results */
}

Yes, I misunderstood the task. I thought topicstarter come from a country where the decimal point is written with a comma (as in Russia).