How to write files in linux

How to write files in Linux:

1. Use fwrite function

Function function

Use to read and write a data block.

General calling form

fwrite(buffer,size,count,fp);

Explanation

(1) buffer: It is a pointer. For fread, it is the storage address of the read data. For fwrite, it is the address of the data to be output.

(2) size: the number of bytes to be read and written;

(3) count: how many size bytes of data items to be read and written;

( 4) fp: file pointer

Example:

A program that writes the current time into text.

int markfile(void )
{
    FILE *sp ;
//    char buff[512] ;
    char count = 0;
    char *currentime = NULL;
    char *wday[] = {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
    time_t timep;
    struct tm *p;
    time(&timep);
    p = localtime(&timep);
    currentime = ctime(&timep);
//    memset(buff,0,512);
//    sprintf(buff,"%s",currentime);
    printf("%d/%d/%d",(1900+p->tm_year),(1+p->tm_mon),p->tm_mday);
    printf(" %s %d:%d:%d\n",wday[p->tm_wday],p->tm_hour,p->tm_min,p->tm_sec);
    if((sp = fopen("/root/kay/mark.txt","a+")) == NULL)
       return 0;
    fwrite(currentime,size(currentime)-1,1,sp);
    fclose(sp);
    return 1;
}

2. Use the echo command

The command format is as follows:

[root@localhost ~]# echo [选项] [输出内容]

Options:

-e: Supports character conversion controlled by backslash (see Table 1 for details)

-n: Cancel the newline symbol at the end of the line after output (no line break after the content is output)

Example:

echo 'i love u' >a.txt  *在a.txt这个文件中输入i love u，如果没有这个文件则创建。如果有这个文件，那么
新内容代替原来的内容。

Recommended learning: linux tutorial

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