/* a simple `cat` program
 * aim:
 * 1. catf
 * 2. catf file_in1 file_in2 ...
 * 3. catf -o file_out
 * 4. catf -o file_out file_in1 file_in2 ...
 */

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

#define LEN 4096

//read in the content of stream `in`, write to stream `out`.
void ReadAndWriteFile(FILE * in, FILE * out);
//close stream `pf`. the `name` of file is passed to assist printing error message
void CloseFile(FILE * pf, char * name);

int main(int argc, char *argv[])
{
    FILE *in, *out;         //in/out file pointer
    int i;

    if( argc==1 )           //func 1: if only `ccat` is given, read in from `stdin` and print out to `stdout`.
    {
        ReadAndWriteFile(stdin, stdout);
    }
    else if( argv[1][0]=='-' )  //func 3,4: if `-` arg is given, prepare a file for output
    {
        if( strcmp(argv[1], "-o")!=0 )  //check validity
        {
            fprintf(stderr, "%s: argument '%s' can not be recognized.\n" , argv[0], argv[1]);
            exit(EXIT_FAILURE);
        }

        if( (out=fopen(argv[2], "a"))==NULL )   //open the output file in `append` mode
        {
            fprintf(stderr, "can not open file '%s' for appending.\n" , argv[2]);
            exit(EXIT_FAILURE);
        }

        if( argc==3 )       //func 3: if no input file, read from stdin
        {
            ReadAndWriteFile(stdin, out);
            CloseFile(out, argv[2]);
        }
        else            //func 4: otherwise read in every input file and write its content to output file
        {
            for( i=3 ; i<argc ; i++ )
            {
                if( (in=fopen(argv[i], "r"))==NULL )    //open every input file in `read` mode
                {
                    fprintf(stderr, "can not open file '%s' for reading.\n" , argv[i]);
                    exit(EXIT_FAILURE);
                }

                ReadAndWriteFile(in, out);
                CloseFile(in, argv[i]);
            }
            CloseFile(out, argv[2]);
        }
    }
    else                //func 2: if no output file, open input files for reading and write to stdout
    {
        for( i=1 ; i<argc ; i++ )
        {
            if( (in=fopen(argv[i], "r"))==NULL )
            {
                fprintf(stderr, "can not open file '%s' for reading.\n" , argv[i]);
                exit(EXIT_FAILURE);
            }

            ReadAndWriteFile(in, stdout);
            CloseFile(in, argv[i]);
        }
    }

    return 0;
}

void CloseFile(FILE * pf, char * name)
{
    if( fclose(pf)!=0 )
    {
        fprintf(stderr, "file '%s' didn't closed successfully.\n" , name);
        exit(EXIT_FAILURE);
    }
}

void ReadAndWriteFile(FILE * in, FILE * out)
{
    static char buffer[LEN];
    while( fgets(buffer, LEN, in)!=NULL )
    {
        fputs(buffer, out);
    }
}

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

int main(int argc, char **argv)
{
    FILE *file;         //file stream to be counted
    int cc=0, wc=0, lc=0;       //char, word, line count
    char ch;            //store input char

    if( argc<2 )            //if no input file, use stdin
    {
        file=stdin;
    }
    else if( (file=fopen(argv[1], "r"))==NULL)  //if there is input file, open it
    {
        fprintf(stderr, "file %s open error.\n" , argv[1]);
        exit(EXIT_FAILURE);
    }
    //cc. every byte counts for a character
    //wc. every alpha-numeric combination counts for a word
    //lc. every '\n' indicates a complete line
    while ( (ch=getc(file))!=EOF )
    {
        if( isalnum(ch) )           //idea is: encountering an alnum char indicates entering a word, wc++,
        {                   //then characters of the word is counted by inner loop
            wc++;               //other characters are counted by outer loop
        }                   //lines and EOF are checked by outer loop
        while( isalnum(ch) )
        {
            cc++;
            ch=getc(file);
        }
        if( ch=='\n' )
        {
            lc++;
        }
        if( ch==EOF )
            break;
        cc++;
    }
    fclose(file);
    printf( "characters: %d\nwords: %d\nlines: %d\n" , cc, wc, lc );

    return 0;
}