在Linux中使用C，通过系统调用将两个文本文件合并为一个新文件（来回换行）

Question

So the assignment is merging two text files in Linux using system calls:

• 1.txt:

Hello,

my class!

• 2.txt:

Today is

a very nice

day

• NEW.txt:

Today is

Hello,

a very nice

my class!

day

Problem is I get (sorry for putting this as code sample):

Hello,
+Today is
my class!


a very nice

day

The + sign keeps changing between ("#", "(", "0", "_", ..) with each execution..

Why do I have extra new lines and this thing with the *? Thank you in advance.

My code:

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

int main(int argc, char* argv[])
{
int p1,p2,pNEW;
char Buff1[1], Buff2[1];
p1=open(argv[1],O_RDONLY);
p2=open(argv[2],O_RDONLY);
pNEW=open(argv[3],O_WRONLY|O_CREAT,0644);

while(read(p1,&Buff1,1)>0 || read(p2,&Buff2,1)>0)
{
    do{
        write(pNEW,&Buff1,1);
        if((Buff1[0]=='\n'))
            break;
    }while(read(p1,&Buff1,1)>0);

    do{
        write(pNEW,&Buff2,1);
        if((Buff2[0]=='\n'))
            break;
    }while(read(p2,&Buff2,1)>0);
}

close(p1);
close(p2);
close(pNEW);
}

Answer 1

you have to retain if you have read all your file or not, because the read in the first while will ... read, and that's not what you want.

Code edited after comment :

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <stdbool.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

bool WriteLineFromFile(int dst, int src, bool *srcTerminated)
{
    int     lastChar    = EOF;
    char    currentChar;
    ssize_t nbCharRead;
    ssize_t nbCharWrite;

    do {
        if ((nbCharRead = read(src, &currentChar, 1)) < 0) {
            fprintf(stderr, "%s : read(src, &buf, 1) : src=%d, errno='%s'.\n", __func__, src, strerror(errno));
            return (false);
        }
        // End of file
        if (nbCharRead == 0) {
            (*srcTerminated) = true;
            // Adding '\n' if necessary
            if (lastChar != '\n' && lastChar != EOF) {
                currentChar = '\n';
                while ((nbCharWrite = write(dst, &currentChar, 1)) != 1) {
                    if (nbCharWrite < 0) {
                        fprintf(stderr, "%s :  write(dst, &buf, 1) : dst=%d, errno='%s'.\n", __func__, dst, strerror(errno));
                        return (false);
                    }
                    sleep(1);
                }
            }
            return (true);
        }
        // Writing a char into the dst file
        while ((nbCharWrite = write(dst, &currentChar, 1)) != 1) {
            if (nbCharWrite < 0) {
                fprintf(stderr, "%s :  write(dst, &buf, 1) : dst=%d, errno='%s'.\n", __func__, dst, strerror(errno));
                return (false);
            }
            sleep(1);
        }
        lastChar = currentChar;
    } while (currentChar != '\n');

    return (true);
}

bool FileMerging(char *inputPathFile1, char *inputPathFile2, char *outputPathFile)
{
    int  inputFile1      = -1;
    bool file1Terminated = false;
    int  inputFile2      = -1;
    bool file2Terminated = false;
    int  outputFile      = -1;
    bool returnFunction  = false;

    // Openning all the file descriptor
    if ((inputFile1 = open(inputPathFile1, O_RDONLY)) == -1) {
        fprintf(stderr, "%s : open(inputPathFile1, O_RDONLY) : inputPathFile1='%s', errno='%s'.\n", __func__, inputPathFile1, strerror(errno));
        goto END_FUNCTION;
    }
    if ((inputFile2 = open(inputPathFile2, O_RDONLY)) == -1) {
        fprintf(stderr, "%s : open(inputPathFile2, O_RDONLY) : inputPathFile2='%s', errno='%s'.\n", __func__, inputPathFile2, strerror(errno));
        goto END_FUNCTION;
    }
    if ((outputFile = open(outputPathFile, O_WRONLY | O_CREAT, 0644)) == -1) {
        fprintf(stderr, "%s : open(outputPathFile, O_RDONLY) : outputPathFile='%s', errno='%s'.\n", __func__, outputPathFile, strerror(errno));
        goto END_FUNCTION;
    }

    // Alternativly print a line from inputFile1 and inputFile2 to outputFile
    do {
        if (!file1Terminated) {
            if (!WriteLineFromFile(outputFile, inputFile1, &file1Terminated)) {
                goto END_FUNCTION;
            }
        }
        if (!file2Terminated) {
            if (!WriteLineFromFile(outputFile, inputFile2, &file2Terminated)) {
                goto END_FUNCTION;
            }
        }
    } while (!file1Terminated || !file2Terminated);


    returnFunction = true;
    /* GOTO */END_FUNCTION:
    if (inputFile1 != -1) {
        close(inputFile1);
    }
    if (inputFile2 != -1) {
        close(inputFile2);
    }
    if (outputFile != -1) {
        close(outputFile);
    }
    return (returnFunction);
}

int main(int argc, char *argv[])
{
    if (argc != 4) {
        fprintf(stderr, "This program wait 3 arguments on the command-line : inputFilePath1 inputPathFile2 outputPathFile.\n");
        return (EXIT_FAILURE);
    }
    if (!FileMerging(argv[1], argv[2], argv[3])) {
        return (EXIT_FAILURE);
    }
    return (EXIT_SUCCESS);
}