I am having a problem with the below code validating a file using regex. My file must only contain letters or numbers. My regular expression is:
#define to_find "^[a-zA-Z0-9]+$"
which is located in my main.h file. The below code is in my main.c
#include <ctype.h>
#include <errno.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include "main.h"
int main(int argc, char * argv[])
{
int ret_val;
regex_t regex;
FILE *fp;
char line[1024];
if (regcomp(®ex, to_find, REG_EXTENDED) != 0)
{
fprintf(stderr, "Failed to compile regex '%s'\n", to_find);
return EXIT_FAILURE;
}
if (argc > 2)
{
printf("Usage: tree OR tree [filename]\n");
return EXIT_FAILURE;
}
else if (argc == 2)
{
fp = fopen(strcat(argv[1],".dat"), "r");
printf("file opened\n");
while ((fgets(line, 1024, fp)) != NULL)
{
line[strlen(line) - 1] = '\0';
if ((ret_val = regexec(®ex, line, 0, NULL, 0)) != 0);
{
printf("Error: %s\n", line);
return EXIT_FAILURE;
}
}
fclose(fp);
printf("File closed\n");
}
return 0;
}
My file I am reading is called names.dat and contains:
int
char
[
double
What is happening is it is kicking out at the very first line which it should kick out at the 3rd line. I am sure this is pretty simple to solve but it seems I have not figured it out. I would appreciate any help. Also, how do I deal with the
\n
character in the file? this file will have several lines. Thanks in advance.
You have some small errors but the one that cause the error is:
// Do you see this sweet little semicolon :P ----------------+
if ((ret_val = regexec(®ex, line, 0, NULL, 0)) != 0); // <+
{
printf("Error: %s\n", line);
return EXIT_FAILURE;
}
beside this line:
fp = fopen(strcat(argv[1],".dat"), "r");
You cannot add to argv, you need to create a new buffer to hold the data, create a buffer with PATH_MAX size add append the path to it. Here an improved version:
#include <ctype.h>
#include <errno.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <limits.h>
#define to_find "^[a-zA-Z0-9]+$"
int main(int argc, char * argv[])
{
int ret_val;
regex_t regex;
FILE *fp;
char file[PATH_MAX];
char line[1024];
if (regcomp(®ex, to_find, REG_EXTENDED) != 0)
{
fprintf(stderr, "Failed to compile regex '%s'\n", to_find);
return EXIT_FAILURE;
}
if (argc > 2)
{
printf("Usage: tree OR tree [filename]\n");
return EXIT_FAILURE;
}
else if (argc == 2)
{
sprintf(file, "%s.dat", argv[1]);
fp = fopen(file, "r");
if( fp == NULL ) {
perror("Error");
return -1;
}
printf("file opened\n");
while (fscanf(fp, "%1023s", line) > 0)
{
if ((ret_val = regexec(®ex, line, 0, NULL, 0)) != 0)
{
printf("Not match: %s\n", line);
//return EXIT_FAILURE;
} else {
printf("Match: %s\n", line);
}
}
regfree(®ex);
fclose(fp);
printf("File closed\n");
}
return 0;
}
See the diff: http://www.diffchecker.com/8itbz5dy
test:
$ gcc -Wall sample.c
$
$ cat name.dat
int
char
[
double
$ ./a.out name
file opened
Match: int
Match: char
Not match: [
Match: double
File closed
$
Related
WHAT I HAVE TO DO
I have to find, starting from a directory, a file located in one of all directories that have as root the directory passed in input.
Something as shell command find.
INPUT/OUTPUT
Having this in input:
./myfind /home/claudio/Scrivania file.txt
I need something as this in output, absolute path and last modify date ecc:
/home/claudio/Scrivania/SistemiOperativi/file.txt Tue Mar 30 19:51:54 2021
MY CODE
It doesn't print anything.
#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <errno.h>
#if !defined(NAME_MAX)
#define NAME_MAX 256
#endif
void find(const char* passed_dir_name, const char* passed_file_name) {
if (chdir(passed_dir_name) == -1) {
perror("FATAL ERROR CHANGING DIRECTORY");
exit(EXIT_FAILURE);
}
DIR* current_directory;
if ((current_directory = opendir(".")) == NULL) {
perror("FATAL ERROR OPENING CURRENT WORKING DIRECTORY");
exit(EXIT_FAILURE);
}
char* buf;
if ((buf = calloc(NAME_MAX, sizeof(char))) == NULL) {
perror("FATAL ERROR ALLOCATING MEMORY");
exit(EXIT_FAILURE);
}
struct dirent* dir;
while ((dir = readdir(current_directory)) != NULL) {
struct stat statbuf;
stat(dir->d_name, &statbuf);
if (S_ISDIR(statbuf.st_mode)) {
if (strncmp(dir->d_name, ".", 1) != 0 && strncmp(dir->d_name, "..", 2) != 0) {
find(dir->d_name, passed_file_name);
}
} else {
if (strncmp(dir->d_name, passed_file_name, strlen(passed_file_name) == 0)) {
if (getcwd(buf, NAME_MAX) == NULL) {
perror("FATAL ERROR");
exit(EXIT_FAILURE);
}
fprintf(stdout, "%s/%s %s", buf, dir->d_name, ctime(&statbuf.st_mtime));
}
}
}
if (closedir(current_directory) == -1) {
perror("FATAL ERROR CLOSING CURRENT WORKING DIRECTORY");
exit(EXIT_FAILURE);
}
chdir("..");
free(buf);
}
int main(int argc, char** argv) {
if (argc != 3) {
fprintf(stderr, "ERROR: RUn as ./myfind directory\n");
exit(EXIT_FAILURE);
}
const char* dir = argv[1];
const char* file = argv[2];
struct stat statbuf;
stat(dir, &statbuf);
if(!S_ISDIR(statbuf.st_mode)) {
fprintf(stderr, "FATAL ERROR: %s IS NOT A DIRECTORY\n", dir);
exit(EXIT_FAILURE);
}
find(dir, file);
exit(EXIT_SUCCESS);
}
Your parentheses are wrong in:
if (strncmp(dir->d_name, passed_file_name, strlen(passed_file_name) == 0))
You need to write:
if (strncmp(dir->d_name, passed_file_name, strlen(passed_file_name)) == 0)
Since strncmp(x, y, 0) will always return 0, the condition is never being met.
But note that there's no point in using strncmp here at all. strncmp is only needed if you don't know that one of your entries is a null terminated string. You have a guarante that d_name is null-terminated, and if passed_file_name is not, then strlen is going to be problematic. You might as well just write strcmp(dir->d_name, passed_file_name).
I wrote this little program that reads a file in binary form (Databases.db in this example) and copies its content in the cpydatabases.db...
When I run the debugger in the fopen_s(&source, "Databases.db", "r");, the source is always NULL (while debugging it shows that the memory entry is always Null, 0x000000000000 <NULL>).
This program runs in visual studio 2015.
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include "dirent.h"
#include <string.h>
#include <sys/stat.h>
#include <stdlib.h>
#define BUFFSIZE 2048
char ch, *readbuf;
int nread, nwrit;
FILE *source, *target;
int main()
{
int returnv;
fopen_s(&source, "Databases.db", "r");
if ( source !== NULL)
{
fclose(source);
return (EXIT_FAILURE);
}
fopen_s(&target,"cpydatabases.db", "w");
//check again
if (target == NULL)
{
fclose(target);
return(EXIT_FAILURE);
}
//setting the char that reads the binary
readbuf = (char *)malloc(BUFFSIZE* sizeof(char));
if (readbuf == NULL)
{
fclose(source);
fclose(target);
return(EXIT_FAILURE);
}
while (1)
{
nread = fread((void *)readbuf, sizeof(char), BUFFSIZE, source) ;
// fwrite((void *)readbuf, sizeof(char), nread, target);
nwrit = fwrite((void *)readbuf, sizeof(char), nread, target);
if (nwrit < nread)
{
returnv = (EXIT_FAILURE);
}
if (nread <= BUFFSIZE)
{
returnv = (EXIT_SUCCESS);
break;
}
}
fclose(source);
fclose(target);
return 0;
}
This worked for me. You should have your Databases.db file in the same folder as your source.cpp file, or use an absolute path like "C:/Databases". Anyway this code worked for me:
#define BUFFSIZE 2048
char ch, source_file[50], target_file[50], *readbuf;
int nread, nwrit;
FILE *source, *target;
int main()
{
int returnv;
fopen_s(&source, "Databases.db", "r");
if (source == NULL)
{
//fclose(source);
return (EXIT_FAILURE);
}
fopen_s(&target, "cpydatabases.db", "w");
//check again
if (target == NULL)
{
fclose(target);
return(EXIT_FAILURE);
}
I think "Databases.db" is in not in same directory where executable is.
You can give complete path of "Databases.db" or copy this file where your .sln file is.
The following code is supposed to work as follows: print the list of the files in a directory, and print the content of each .c file.
it works fine when executed in UNIX for the same directory: ./a.out ./
However, I was not able to make it work for ./a.out ../differentDir execution.
I know that if the absolute path is provided as an argument, I could use argv[1] for that. However, when it is provided in a form of a relative path I am lost.
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define BUFFSIZE 32768
int main(int argc, char **argv) {
char buf[BUFFSIZE];
DIR *dp;
struct dirent *dirp;
char filename[80];
int name_length;
FILE *fp;
if (argc != 2) {
fprintf(stderr, "usage: %s dir_name\n", argv[0]);
exit(1);
}
if ((dp = opendir(argv[1])) == NULL ) {
fprintf(stderr, "can't open '%s'\n", argv[1]);
exit(1);
}
while ((dirp = readdir(dp)) != NULL ){
printf("%s\n", dirp->d_name);
memset(filename, '\0', sizeof(filename));
strcpy(filename, dirp->d_name);
printf(" ** %s ", filename);
name_length = strlen(filename);
printf(" name_length=%d \n", name_length);
if (findC(filename)) // checking if the file has a .c extension
{
fp=fopen(filename, "r");
if (fp == NULL)
fprintf(stderr, "Can't open .C file!\n");
else
{// if the file was opened successfuly:
do
{
fgets(buf,BUFFSIZE,fp); // reading each line until buffer is full or until reaching whitespace
buf[strlen(buf)-1]='\0'; // removing the trailing whitespace from the buffer
puts(buf);
}
while (!feof(fp));
printf("\n\n");
fclose(fp);
}
}
}
closedir(dp);
return(0);
}
/*FindC method gets a c-string that represents a file name; returns 1 if the file ends with .C extension, else returns 0*/
int findC(char * name)
{
int len = strlen(name);
if (len>=2 && name[len-2]=='.' && tolower(name[len-1])=='c')
return 1;
return 0;
}
Upon opening the file to read, the file pathname needs to also be relative.
// Form prefix for complete relative file name
char filename[MAXPATH];
strcpy(filename, argv[1]);
// append '/' if directory path does not end in '/'
if (TBD_code(filename)) {
strcat(filename, "/");
}
char *end = filename[strlen(filename)];
while ((dirp = readdir(dp)) != NULL ){
printf("%s\n", dirp->d_name);
if (findC(dirp->d_name)) {
// append filename to prefix
strcpy(end, dirp->d_name);
fp=fopen(filename, "r");
...
You can use realpath(argv1...) like in this example. realpath will return the absolute path for a relative path.
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
int main(int argc, char **argv) {
char *path = "../..";
char buff[PATH_MAX + 1]; /* not sure about the "+ 1" */
char *res = realpath(path, buff);
if (res) {
printf("This source is at %s.\n", buff);
} else {
perror("realpath");
exit(EXIT_FAILURE);
}
return 0;
}
To include the desired behavior in your program, you can use realpathin your code:
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <ctype.h>
#include <dirent.h>
#include <string.h>
#define BUFFSIZE 32768
int main(int argc, char **argv) {
char buf[BUFFSIZE];
DIR *dp;
struct dirent *dirp;
char filename[80];
int name_length;
FILE *fp;
char buff[PATH_MAX + 1]; /* not sure about the "+ 1" */
if (argc != 2) {
fprintf(stderr, "usage: %s dir_name\n", argv[0]);
exit(1);
}
char *res = realpath(argv[1], buff);
if ((dp = opendir(res)) == NULL ) {
fprintf(stderr, "can't open '%s'\n", argv[1]);
exit(1);
}
while ((dirp = readdir(dp)) != NULL ){
printf("%s\n", dirp->d_name);
memset(filename, '\0', sizeof(filename));
strcpy(filename, dirp->d_name);
printf(" ** %s ", filename);
name_length = strlen(filename);
printf(" name_length=%d \n", name_length);
if (findC(filename)) // checking if the file has a .c extension
{
fp=fopen(filename, "r");
if (fp == NULL)
fprintf(stderr, "Can't open .C file!\n");
else
{// if the file was opened successfuly:
do
{
fgets(buf,BUFFSIZE,fp); // reading each line until buffer is full or until reaching whitespace
buf[strlen(buf)-1]='\0'; // removing the trailing whitespace from the buffer
puts(buf);
}
while (!feof(fp));
printf("\n\n");
fclose(fp);
}
}
}
closedir(dp);
return(0);
}
/*FindC method gets a c-string that represents a file name; returns 1 if the file ends with .C extension, else returns 0*/
int findC(char * name)
{
int len = strlen(name);
if (len>=2 && name[len-2]=='.' && tolower(name[len-1])=='c')
return 1;
return 0;
}
You could first change to the directory chdir either with relative or absolute path and the get the absolute path via the getcwd
#include <sys/types.h>
#include <string.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define BUFFSIZE 32768
#define PATH_SIZE 512
int main(int argc, char **argv) {
char buf[BUFFSIZE];
char path[PATH_SIZE];
DIR *dp;
struct dirent *dirp;
char filename[80];
int name_length, r;
FILE *fp;
if (argc != 2) {
fprintf(stderr, "usage: %s dir_name\n", argv[0]);
exit(1);
}
strcpy(path, argv[1]);
r = chdir(path);
if( r != 0 )
{
printf("Invalid path '%s'\n",path);
exit(1);
}
getcwd(path,PATH_SIZE);
if ((dp = opendir(path)) == NULL ) {
fprintf(stderr, "can't open '%s'\n", argv[1]);
exit(1);
}
while ((dirp = readdir(dp)) != NULL ){
printf("%s\n", dirp->d_name);
memset(filename, '\0', sizeof(filename));
strcpy(filename, dirp->d_name);
printf(" ** %s ", filename);
name_length = strlen(filename);
printf(" name_length=%d \n", name_length);
if (findC(filename)) // checking if the file has a .c extension
{
fp=fopen(filename, "r");
if (fp == NULL)
fprintf(stderr, "Can't open .C file!\n");
else
{// if the file was opened successfuly:
do
{
fgets(buf,BUFFSIZE,fp); // reading each line until buffer is full or until reaching whitespace
buf[strlen(buf)-1]='\0'; // removing the trailing whitespace from the buffer
puts(buf);
}
while (!feof(fp));
printf("\n\n");
fclose(fp);
}
}
}
closedir(dp);
return(0);
}
/*FindC method gets a c-string that represents a file name; returns 1 if the file ends with .C extension, else returns 0*/
int findC(char * name)
{
int len = strlen(name);
if (len>=2 && name[len-2]=='.' && tolower(name[len-1])=='c')
return 1;
return 0;
}
I am having trouble compiling my program.
The error message is: undefined reference to `_fcloseall', I think it could be a missing library file at the beginning. It might be also useful to know that I am programming on Windows 8.1 + Cygwin. Which library could be missing or do you see any other mistake?
Here is the code:
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
void cleanup1();
void cleanup2();
int main(int argc, char *argv[])
{
FILE * file;
if(argc < 2){
printf("\ncommand bsp10085 <file>");
exit(1);
}
assert(atexit(cleanup1) == 0);
assert(atexit(cleanup2) == 0);
if((datei = fopen(argv[1], "r")) != NULL){
printf("\nfile %s is being processed ..",argv[1]);
fclose(datei);
}
else
printf("\nfile '%s' is missing. ", argv[1]);
}
void cleanup1(){
printf("\nCleanup the rest");
}
void cleanup2(){
printf("\nClose all open files");
fflush(NULL);
_fcloseall();
}
I tried to compile your code (in ubuntu though) and i also got a warning: warning: implicit declaration of function ‘fcloseall’ [-Wimplicit-function-declaration] fcloseall();
I think that if you add
#define _GNU_SOURCE
before
#include<stdio.h>
your program should work fine. This is your code after i changed some other warnings as well:
#define _GNU_SOURCE
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
void cleanup1();
void cleanup2();
int main(int argc, char *argv[])
{
FILE *datei;
if(argc < 2){
printf("\ncommand bsp10085 <file>");
exit(1);
}
assert(atexit(cleanup1) == 0);
assert(atexit(cleanup2) == 0);
if((datei = fopen(argv[1], "r")) != NULL){
printf("\nfile %s is being processed ..",argv[1]);
fclose(datei);
}
else
printf("\nfile '%s' is missing. ", argv[1]);
return 0;
}
void cleanup1(){
printf("\nCleanup the rest");
}
void cleanup2(){
printf("\nClose all open files");
fflush(NULL);
fcloseall();
}
how can i use Regex Expressions in C programming?
for example if i want to find a line in a file
DAEMONS=(sysklogd network sshd !netfs !crond)
then print each daemon in separate line like this
sysklogd
network
sshd
!netfs
!crond
here what i did so far
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <regex.h>
#define tofind "[a-z A-Z] $"
int main(){
FILE *fp;
char line[1024];
int retval = 0;
char address[256];
regex_t re;
if(regcomp(&re, tofind, REG_EXTENDED) != 0)
return;
fp = fopen("/etc/rc.conf","r");//this file has this line "DAEMONS=(sysklogd network sshd !netfs !crond)"
while((fgets(line, 1024, fp)) != NULL) {
if((retval = regexec(&re, address, 0, NULL, 0)) == 0)
printf("%s\n", address);
}
}
Any help would be much appreciated.
You read the line into line, so you should pass line to regexec(). You also need to think about whether the newline at the end of the line affects the patterns. (It was correct to use fgets(), but remember it keeps the newline at the end.)
You should also do return -1; (or any other value that is not 0 modulo 256) rather than a plain return with no value. Also, you should check that the file was opened; I had to use an alternative name because there is no such file as /etc/rc.conf on my machine - MacOS X.
This works for me:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <regex.h>
#define tofind "[a-z A-Z] $"
int main(int argc, char **argv)
{
FILE *fp;
char line[1024];
int retval = 0;
regex_t re;
//this file has this line "DAEMONS=(sysklogd network sshd !netfs !crond)"
const char *filename = "/etc/rc.conf";
if (argc > 1)
filename = argv[1];
if (regcomp(&re, tofind, REG_EXTENDED) != 0)
{
fprintf(stderr, "Failed to compile regex '%s'\n", tofind);
return EXIT_FAILURE;
}
fp = fopen(filename, "r");
if (fp == 0)
{
fprintf(stderr, "Failed to open file %s (%d: %s)\n",
filename, errno, strerror(errno));
return EXIT_FAILURE;
}
while ((fgets(line, 1024, fp)) != NULL)
{
line[strlen(line)-1] = '\0';
if ((retval = regexec(&re, line, 0, NULL, 0)) == 0)
printf("<<%s>>\n", line);
}
return EXIT_SUCCESS;
}
If you need help writing regular expressions instead of help writing C code that uses them, then we need to design the regex to match the line you show.
^DAEMONS=([^)]*) *$
This will match the line as long as it is written as shown. If you can have spaces between the 'S' and the '=' or between the '=' and the '(', then you need appropriate modifications. I've allowed for trailing blanks - people are often sloppy; but if they use trailing tabs, then the line won't be selected.
Once you've found the line, you have to split it into pieces. You might elect to use the 'capturing' brackets facility, or simply use strchr() to find the open bracket, and then a suitable technique for separating the daemon names - I'd avoid strtok() and probably use strspn() or strcspn() to find the words.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <regex.h>
#define tofind "^DAEMONS=\\(([^)]*)\\)[ \t]*$"
int main(int argc, char **argv)
{
FILE *fp;
char line[1024];
int retval = 0;
regex_t re;
regmatch_t rm[2];
//this file has this line "DAEMONS=(sysklogd network sshd !netfs !crond)"
const char *filename = "/etc/rc.conf";
if (argc > 1)
filename = argv[1];
if (regcomp(&re, tofind, REG_EXTENDED) != 0)
{
fprintf(stderr, "Failed to compile regex '%s'\n", tofind);
return EXIT_FAILURE;
}
fp = fopen(filename, "r");
if (fp == 0)
{
fprintf(stderr, "Failed to open file %s (%d: %s)\n", filename, errno, strerror(errno));
return EXIT_FAILURE;
}
while ((fgets(line, 1024, fp)) != NULL)
{
line[strlen(line)-1] = '\0';
if ((retval = regexec(&re, line, 2, rm, 0)) == 0)
{
printf("<<%s>>\n", line);
printf("Line: <<%.*s>>\n", (int)(rm[0].rm_eo - rm[0].rm_so), line + rm[0].rm_so);
printf("Text: <<%.*s>>\n", (int)(rm[1].rm_eo - rm[1].rm_so), line + rm[1].rm_so);
char *src = line + rm[1].rm_so;
char *end = line + rm[1].rm_eo;
while (src < end)
{
size_t len = strcspn(src, " ");
if (src + len > end)
len = end - src;
printf("Name: <<%.*s>>\n", (int)len, src);
src += len;
src += strspn(src, " ");
}
}
}
return EXIT_SUCCESS;
}
A good deal of debugging code in there - but it won't take you long to produce the answer you request. I get:
<<DAEMONS=(sysklogd network sshd !netfs !crond)>>
Line: <<DAEMONS=(sysklogd network sshd !netfs !crond)>>
Text: <<sysklogd network sshd !netfs !crond>>
Name: <<sysklogd>>
Name: <<network>>
Name: <<sshd>>
Name: <<!netfs>>
Name: <<!crond>>
Beware: when you want a backslash in a regex, you have to write two backslashes in the C source code.