Call system UNIX - File copy in C -


i try create copy of source file target file empty.

the algorithm is: read stdin , write source file, read on file , write text in target file.

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h>  #define buffsize 8192  int main(){     int fdsource, fdtarget;     int n, nr;     char buff[buffsize];      fdsource = open("source.txt", o_rdwr | o_creat, s_irusr | s_iwusr); // create , open source file in read/write     if (fdsource < 0){         printf("source file open error!\n");         exit(1);     }      fdtarget = open("target.txt", o_wronly | o_creat, s_irusr | s_iwusr); // create , open source file in write     if (fdtarget < 0){         printf("target file open error!\n");         exit(1);     }      printf("\ninsert text:\n");     while ((n = read(stdin_fileno, buff, buffsize)) > 0){ // read stdin , write source file         if ((write(fdsource, buff, n)) != n){             printf("source file write error!\n");             exit(1);         }     }      while ((read(fdsource, buff, n)) > 0){ // read source file , write target file         if ((write(fdtarget, buff, n)) != n){             printf("source file open error!\n");             exit(1);         }     }     close(fdsource);     close(fdtarget);     exit(0);     return 0; }

the problem code "you have opened both file in initial stage". solve problem open source file in write mode , write data, close , reopen source file in read mode, open target file in write mode. modified code given below , not tested

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h>  #define buffsize 8192  int main(){     int fdsource, fdtarget;     int n;     char buff[buffsize];      fdsource = open("source.txt", o_rdwr | o_creat, s_irusr | s_iwusr); // create , open source file in read/write     if (fdsource < 0){         printf("source file open error!\n");         exit(1);     }     printf("\ninsert text:\n");     while ((n = read(stdin_fileno, buff, buffsize)) > 0){ // read stdin , write source file         if ((write(fdsource, buff, n)) != n){             printf("source file write error!\n");             exit(1);         }     }      close(fdsource);     fdsource = open("source.txt", o_rdwr | o_creat, s_irusr | s_iwusr); // create , open source file in read/write     if (fdsource < 0){         printf("source file open error!\n");         exit(1);     }      fdtarget = open("target.txt", o_wronly | o_creat, s_irusr | s_iwusr); // create , open source file in write     if (fdtarget < 0){         printf("target file open error!\n");         exit(1);     }      while ((read(fdsource, buff, n)) > 0){ // read source file , write target file         if ((write(fdtarget, buff, n)) != n){             printf("source file open error!\n");             exit(1);         }     }     close(fdsource);     close(fdtarget);     exit(0);     return 0; }

if wrong anywhere use logic mentioned above.


Comments

Post a Comment

Popular posts from this blog

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

php - Nothing but 'run(); ' when browsing to my local project, how do I fix this? -

i added new project. made mistake in projectname.conf file in sites-available apache2, led me reinstalling apache2. after reinstalling , re-enabling projects on every page of every project .. <body> run(); </body> .. i've run composer update, restarted service, restarted pc, checked config files, tried disabling new project. there nothing in error log, , access.log: 127.0.0.1 - - [15/may/2015:01:40:47 +0200] "get / http/1.1" 304 181 "-" "mozilla/5.0 (x11; ubuntu; linux x86_64; rv:38.0) gecko/20100101 firefox/38.0" maybe i'm forgetting apache2 reinstall? don't think did different last time installed it. looks haven't setup php correctly. take @ this great guide , maybe you're forgetting link php config apache2.
Read more

php - How can I echo out this array? -

i don't know how go grabbing data in variable , put foreach loop. class tree{ private $info = array( array('name'=>'jim','state'=>'nu','company'=>'nu','phone'=>array('cell'=>'5615111111','office'=>'5611111111'),'email'=>array('primary'=>'exs@example.com','ex@there.com')), array('name'=>'joe smith','city'=>'phoenix','phone'=>'4805551111','email'=>'jsmith@some_email.com'), array('name'=>'john doe','city'=>'chandler','company'=>'doe co.','email'=>array('jdoe@gmail.com','personal'=>'email@email.com'),'phone'=>'6025550002') ); } if you're inside of class, can access private variable using $this->variablename . example, i
Read more