Question

Hello:)
I need someone to translate this little bash script to C because now it consumes way to much CPU and so that i (and other people searching this on google) can learn walking with C! This will be most effective to learn and im planing to do a lot with C but yet iam a programmer of script languages only and know very basic java….

*BASH SCRIPT TO TRANSLASTE TO C*
a1=$1
a2=`expr $a1 + 1`
a3=`expr $a1 + 2`
a4=`expr $a1 + 3`
a5=`expr $a1 + 4`
Limit=`expr $a1  +  99999999999`
while [ $a1 -le $Limit ]
do
echo $a1,$a2,$a3,$a4,$a5 | sed 's/9,/9abc/g' >> List$1
a1=`expr $a1  +  500`  
a2=`expr $a2  +  500`
a3=`expr $a3  +  500`
a4=`expr $a4  +  500`
a5=`expr $a5  +  500`
done

..Thus if i knew the following things in C this would be all for now.

1. handleing the variables
2. euivalent for >> adding to file but perferably with a cache to
   reduce disk io!
3. something euivalent to $1 – allowing the user to set a variable
   when running the C programm.
4. REGEX in C
5. euivalent to | pipe in C
6. Or how to execute a bash command within a C programm since it
   cant get much faster than grep,sed anyways…

Thanks a lot to everyone reading this

Answer 1

Something like this:

#ifdef __cplusplus 
    #include <cstdio>
    #include <cstdlib>
    #include <cstring>
#else
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
#endif

char * stringReplace(char *string, char *search, char *replace) 
{
    char *tempString, *searchStart;
    int len=0;


    // preuefe ob Such-String vorhanden ist
    searchStart = strstr(string, search);
    if(searchStart == NULL) {
        return string;
    }

    // Speicher reservieren
    tempString = (char*) malloc(strlen(string) * sizeof(char));
    if(tempString == NULL) {
        return NULL;
    }

    // temporaere Kopie anlegen
    strcpy(tempString, string);

    // ersten Abschnitt in String setzen
    len = searchStart - string;
    string[len] = '\0';

    // zweiten Abschnitt anhaengen
    strcat(string, replace);

    // dritten Abschnitt anhaengen
    len += strlen(search);
    strcat(string, (char*)tempString+len);

    // Speicher freigeben
    free(tempString);

    return string;
}




int main(int argc, char* argv[])
{
    int i;
    for(i = 0; i < argc; ++i)
        printf("argv[%d]: %s\n", i, argv[i]);

    char string [256];
    int a1 = atoi((const char*) gets(string));
    int a2= a1 +1;
    int a3 = a1 + 2;
    int a4 = a1 + 3;
    int a5 = a1 + 4;

    int limit = a1 + 99999999999;

    while(a1 <= limit)
    {


        char command[1000];

        sprintf(command, "%d,%d,%d,%d,%d", a1, a2, a3, a4, a5);

        stringReplace(command, "9,", "9abc");

        FILE* pFile = fopen ("myfile.txt","wa");
        fprintf (pFile, "%s\n", command);
        fclose (pFile);


        /*
        sprintf(command, "echo \"%d,%d,%d,%d,%d\" | sed 's/9,/9abc/g' >> List%s", a1, a2, a3, a4, a5, string);


        FILE* pPipe  = popen(command, "r");
        char   psBuffer[128];
        while( !feof( pPipe ) )
        {
            if( fgets( psBuffer, 128, pPipe ) != NULL )
                printf("%s\n", psBuffer );
        }

        pclose(pPipe);
        */

        a1 += 500;
        a2 += 500;
        a3 += 500;
        a4 += 500;
        a5 += 500;
    }

    return EXIT_SUCCESS;
}