I have recently begun C and want to open a file, read the content of the file and then write to new file while adding in connector words inside the {} of the text.
However, I am not so sure whether I am getting the set-up for open/read correctly.
For example:
#define MAX_READ 20
int main(int argc, char *argv[]){
char buffer[MAX_READ + 1];
ssize_t numRead;
char connector[2] = ["and", "or"];
if(argc > 1){
int file = open(argv[1], O_RDWR);
if(file == -1){
perror("open");
exit(1);
}
numRead = read(file, buffer, MAX_READ)
if(numRead == -1){
perror("read");
exit(1);
}
}
}
Here is my sample text:
I am running {} swimming together with my friend {} brother
Expected output:
Open the file contents
Read the files content into a variable; match {} and replace each by the connector.
Write the result to a NEW file.
Output:
I am running and swimming together with my friend or brother
Related
//error handle
void my_err(const char* errno_string,int line){
fprintf(stderr,"line:%d ",line);
perror(errno_string);
exit(1);
}
//self-definded read data function
int my_read(int fd){
int len;
int ret;
int i;
char read_buf[64];
//get length of file and keep point of file at the srart
if(lseek(fd,0,SEEK_END) == -1){
my_err("lseek",__LINE__);
}
if((len = lseek(fd,0,SEEK_CUR)) == -1){
my_err("lseek",__LINE__);
}
if(lseek(fd,0,SEEK_SET) == -1){
my_err("lseek",__LINE__);
}
printf("len:%d\n",len);
//read data
if((ret = read(fd,read_buf,len)) < 0){
my_err("read",__LINE__);
}
//print data
for(i = 0;i<len;i++){
printf("%c",read_buf[i]);
}
printf("\n");
return ret;
}
int main()
{
int fd;
char write_buf[32] = "hello boy!";
//create example2 in current directory
if((fd = creat("example2.c",S_IRWXU)) == -1){
// if((fd = open("example2.c",O_RDWR|O_CREAT|O_TRUNC,S_IRWXU)) == -1){
my_err("open",__LINE__);
}else{
printf("craete file success\n");
}
//write data
if(write(fd,write_buf,strlen(write_buf)) != strlen(write_buf)){
my_err("write",__LINE__);
}
my_read(fd);
//Spacing of presentation files
printf("/*------------*/\n");
if(lseek(fd,10,SEEK_END) == -1){
my_err("lseek",__LINE__);
}
if(write(fd,write_buf,strlen(write_buf)) != strlen(write_buf)){
my_err("write",__LINE__);
}
my_read(fd);
close(fd);
return 0;
}
Line 43 is this part of main
//create example2 in current directory
if((fd = creat("example2.c",S_IRWXU)) == -1){
my_err("open",__LINE__);
}else{
printf("craete file success\n");
}
When I use creat, I get an error line:43 read: Bad file descriptor, but I get the correct result with open. Shouldn't both functions return file descriptors? Why should creat return the wrong file descriptor
When I use creat, I get an error line:43 read: Bad file descriptor, but I get the correct result with open. Shouldn't both functions return file descriptors? Why should creat return the wrong file descriptor
Shouldn't both functions return file descriptors?
They should and they do.
Why should creat return the wrong file descriptor
It shouldn't and it doesn't. read fails with Bad file descriptor error, not creat.
creat opens file write-only, so you can't read from it. It's a bad file descriptor if you want to read from it.
The call creat(path, mode) behaves the same as the call open(path, O_CREAT | O_WRONLY | O_TRUNC, mode). On success, the file is opened for writing only. The file descriptor passed to read needs to be open for either reading and writing or for reading only. If the file descriptor is open for writing only, calls to read with that file descriptor will fail. When read fails, the error number EBADF means that the file descriptor is not a valid file descriptor open for reading.
I have created one function which filters data from a data file and prints it to another file using redirection operator of unix
below is the function
void getdetailbyparam(char *name,char *type,int maxprice,int minprice)
{
printf("NAME:%s\nTYPE:%s\nMAX PRICE:%d MIN PRICE:%d\n",name,type,maxprice,minprice);
char getdetailbyparamfilelocation[1024];
snprintf(getdetailbyparamfilelocation, sizeof(getdetailbyparamfilelocation), "\"%s/getdetailbyparam.txt\"",cwd);
char command[1024];
snprintf(command, sizeof(command),"awk -F['|'] '{if (($3 ~ /.*%s.*/) && ($5==\"%s\") && ($7 >= %d) && ($7 <= %d)) print $7,$3,$1}' OFS=\" | \" %s | sort -n > %s",name,type,minprice,maxprice,databasefilelocation,getdetailbyparamfilelocation);
printf("Command is : %s\n",command);
system(command);
printf("File %s created\n",getdetailbyparamfilelocation);
}
Just need to give paths in "getdetailbyparamfilelocation" and "databasefilelocation".
Now When I call this function the file is created but when I try to open this file after calling the function it is giving me error of "No such file or directory"
Please see the following code
void funct(int sock)
{
char getdetailbyparamfilelocation[1024];
snprintf(getdetailbyparamfilelocation, sizeof(getdetailbyparamfilelocation), "\"%s/getdetailbyparam.txt\"",cwd);
size_t len = 0;
ssize_t read;
FILE *fp;
printf("Start sending data from the file at %s\n",getdetailbyparamfilelocation);
char *line = NULL;
fp = fopen(getdetailbyparamfilelocation, "r");
printf("Reading file \n");
if(fp == NULL)
{
perror("Error");
exit(1);
}
while((read = getline(&line, &len, fp)) != -1)
{
char sendline[1024];
int retu;
snprintf(sendline, sizeof(sendline), line);
printf("SERVER SENDING :%s\n",sendline);
retu = send(sock, line, strlen(line), 0);
}
}
Basically I am coding a client server sytem in which server reads the filtered results and send them to client to displays on client's terminal
Please help and also let me know if any further information is required
You need the double quotes around the file name only if you pass it to the shell. You don't need them when passing the file name to fopen.
Instead of
snprintf(getdetailbyparamfilelocation,
sizeof(getdetailbyparamfilelocation),
"\"%s/getdetailbyparam.txt\"",cwd);
Use
snprintf(getdetailbyparamfilelocation,
sizeof(getdetailbyparamfilelocation),
"%s/getdetailbyparam.txt",cwd);
I have created a Client/Server application in C by using the SSL library. the issue i am facing is each time i send a file there are some bytes missing in the start of file.
let suppose the text file which i am sending contains
123456789
and when the client receive the file it would contains
56789
Server-Code
void sendFile(SSL* ssl)
{
char response[2048] = {0};
int read = 0;
FILE* fd;
fd = fopen("snt.txt","rb");
if (fd == NULL)
{
printf("file loading failed\n");
return;
}
while ((read=fread(response,sizeof(char),1024,fd)) > 0)
{
SSL_write(ssl,response,read);
printf("read :%d\n",read);
//puts(response);
//printf("***Data Sent***\n");
memset(response,0,1024);
}
printf("***Data Sent***\n");
fclose(fd);
}
Client Code
FILE *ft;
char filebuf[2048];
int read = 0;
int error_check=0;
ft = fopen("rcv.txt","ab");
if (ft == NULL)
{
printf("Can not open file to write\n");
return -1;
}
memset(filebuf,0,2048);
int cnk=1;
while ((error_check=BIO_read(bio,&read,sizeof(int)))>0)
{
//printf("%d read\n",read);
if (error_check==0)
break;
if (read==0)
break;
BIO_read(bio,filebuf,read);
printf("%d Chunk Recieved\n",cnk++);
//puts(filebuf);
fwrite(filebuf,sizeof(char),strlen(filebuf),ft);
memset(filebuf,0,2048);
}
printf("***File Recieved***");
fclose(ft);
the other issue is client side is not terminated, control doesn't get away from the while-loop, kindly guide me how can i tackle these issues
Assuming size(int) is 4, I'd say the 1st 4 bytes are read by this line:
while ((error_check=BIO_read(bio,&read,sizeof(int)))>0)
That leaves the rest of the data sent to this line:
BIO_read(bio,filebuf,read);
The latter reads it into filebuf which then is written to the file rcv.txt.
So this is one of the first programs I've ever used some self created error checks however for some reason when I compile this and run it using:
./file test1.txt test2.txt 10
I get absolutely an error suggesting that the output file exists and I've checked the file and it doesn't even when I change the name of the output file (second argument) I get nothing. Anyone who can help? I've been racking my brain for ages now. This is a UNIX homework assignment I'm compiling and running in Gentoo. I have it running in a VB and have a linked folder between my windows and linux OS's.
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#define BUFFT 25
int main (int argc, char *argv[])
{
int count;
int readin;
int writeout;
printf ("This program was called \"%s\".\n",argv[0]);
if (argc > 1)
{
for (count = 1; count < argc; count++)
{
printf("argv[%d] = %s\n", count, argv[count]);
}
}
else
{
perror("The command had no arguments.\n");
exit(-1);
}
// check correct number of arguments parsed //
if (argc == 4)
{
printf("There are the correct number of arguments(4)\n");
}
else
{
perror("Not enough arguments! please try again \n");
exit(-1);
}
//Check original file is there//
int openFD = open(argv[1], O_RDWR);
if (openFD <0)
{
perror("Error unable to read file \n");
exit(-1);
}
//Check existence of output file, if it doesn't exist create it//
int CheckFile = open(argv[2], O_RDONLY);
if (CheckFile < 0)
{
perror("Error output file already exists \n");
exit(-1);
}
else
{
int CheckFile = open(argv[2], O_CREAT);
printf("The file has successfully been created \n");
}
//Create buffer
int bufsize = atoi(argv[3]);
char *calbuf;
calbuf = calloc(bufsize, sizeof(char));
//Read text from original file and print to output//
readin = read(openFD, calbuf, BUFFT);
if (readin < 0){
perror("File read error");
exit(-1);
}
writeout = write(openFD,bufsize,readin);
if (writeout <0){
perror("File write error");
exit(-1);
}
return 0;
}
The open call for HANDLE CheckFile is printing Error File Exists. This is your problem. You are printing out the wrong statement when Output File Is Not Found and moreover you are exiting which prevents the code to create any.
int CheckFile = open(argv[2], O_RDONLY);
if (CheckFile < 0)
{
//Means the file doesn't exist
int CheckFile = open(argv[2], O_CREAT);
// Check for errors here
}
And why are you trying to do this::
writeout = write(openFD,bufsize,readin);
when your HANDLE TO OUTPUT FILE IS CheckFile
int CheckFile = open(argv[2], O_RDONLY);
if (CheckFile < 0)
{
perror("Error output file already exists \n");
A negative return from open means that the file could not be opened, most likely because it does not exist ... it does not mean that the file already exists. Failing to open the input file certainly does not mean that the output file already exists. Please check your code more carefully for obvious errors, e.g.,
int CheckFile = open(argv[2], O_CREAT);
printf("The file has successfully been created \n");
Here you don't check the return code.
Take a look at this fragment of your code:
int CheckFile = open(argv[2], O_RDONLY);
if (CheckFile < 0)
{
perror("Error output file already exists \n");
exit(-1);
}
You are saying trying to open a file in READ ONLY MODE. From what I read in your question, it's not an error if the file doesn't exist, but in the code you are validating the opposite, if the file doesn't exists, throw an error (in fact your message error is incorrect here).
Double check your logic and you will find your solution.
code:
int main(int argc, char **argv)
{
int fd = open("test.txt", O_CREAT|O_RDWR, 0200|0400);
if(fd == -1)
{
printf("failure to oepn");
exit(-1);
}
int iRet = write(fd, "aaaaaaaaaa", 10);
if(iRet == -1)
{
printf("failure to writer");
exit(-1);
}
sleep(10);
printf("You must remove");
iRet = write(fd, "bbbbbbbbbb", 10);
if(iRet == -1)
{
printf("failure to after writer");
exit(-1);
}
exit(0);
}
during the sleep(), you delete the test.txt, but the process write successful!why?
if a log ”Singleton“ instance, you remove the file on the disk.write is successful, but you can get nothing.
class log
{
public:
void loggerWriter(std::string str);
int fd;
};
log::log(std::string filename):fd(-1)
{
fd = open(filename.c_str(), O_CREAT|)
//...
}
log::loggerWriter(std::string str)
{
writer(fd, str.c_str(), str.size());
}
int main()
{
log logger("text.txt");
//...
//I want to know the text.txt the text.txt have delete on the disk or not.
//if delete i can create another file to log.
}
"unlink" cann't solve this problem.
The manual page for unlink(2) states clearly:
unlink() deletes a name from the file system. If that name was the
last link to a file and no processes have the file open the file is
deleted and the space it was using is made available for reuse.
If the name was the last link to a file but any processes still have
the file open the file will remain in existence until the last file
descriptor referring to it is closed.
As caf excellently notes in the comments:
The write() is successful because it writes to the file, which still
exists at this point even though it no longer has a name. The filename
and the file itself are distinct, and have separate lifetimes.