C Regex

[matmatmat]

I have this program:


#include <stdio.h>
#include "useful_functions.h"
#define MAXLINE 1000

int main(int argc, char *argv[]){
char line[MAXLINE];
long lineno = 0;
int c, except = 0, number = 0, found = 0, ignore = 0;

while (--argc > 0 && (*++argv)[0] == '-'){
while (c = *++argv[0]){
switch (c) {
case 'x':
except = 1;
break;
case 'n':
number = 1;
break;
case 'i':
ignore = 1;
break;
default:
printf("Illegal option\n");
argc = 0;
found = -1;
}
}
}
FILE *fp;
*++argv;
fp = fopen(*argv, "r");
*argv--;
if (fp == NULL){
while (getline(line, MAXLINE, stdin) > 0){
lineno++;
char oline[MAXLINE];
if (ignore){
copy(oline, line);
strlower(line);
strlower(*argv);
}
if (match(line, *argv)){
if (number){
printf("%ld: ", lineno);
}
if (ignore){
printf("%s", oline);
}else{
printf("%s", line);
}
found++;
}
}
}else{
while(getline(line,MAXLINE, fp) > 0){
lineno++;
char oline[MAXLINE];
if (ignore){
copy(oline, line);
strlower(line);
strlower(*argv);
}
if (match(line, *argv)){
if (number){
printf("%ld: ", lineno);
}
if (ignore){
printf("%s", oline);
}else{
printf("%s", line);
}
found++;
}
}
}
return found;
}


the functions defined in the header file are:


//strcpy clone
void copy(char to[], char from[]){
int i = 0;
while ((to[i] = from[i]) != '\0'){
++i;
}
}

//tolower clone
char lower(char c){
if (c >= 'A' && c <= 'Z'){
return c + 'a' - 'A';
}else{
return c;
}
}

void strlower(char string[]){
int i;
for(i=0;string[i] != '\0';i++){
string[i] = lower(string[i]);
}
}

int getline(char s[], int lim, FILE *f){
int c, i;
for (i=0; i<lim-1 && (c=getc(f))!=EOF && c!='\n'; ++i){
s[i] = c;
}
if (c == '\n'){
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}

int match(const char *string, char *pattern) {
int status;
regex_t re;
if(regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
return 0;
}
status = regexec(&re, string, (size_t)0, NULL, 0);
regfree(&re);
if(status != 0) {
return 0;
}
return 1;
}

when run like this:


ls | /.mgrep .c$

I expect it to print out all files that end with '.c', but it prints nothing

[dwhitney67]

I am not at all familiar with the regex C library functions, however there are some basic errors in your code that perhaps are contributing to your app's woes.

Here's a modified source I built, that unfortunately still exhibits the same issue you reported. It is a bit leaner than the code you presented, and because I use the gnu99 version of GCC, I had to rename getline() to be getLine().



#include "useful_functions.h"
#include <stdio.h>

#define MAXLINE 1000

int main(int argc, char *argv[])
{
long lineno = 0;
int c, except = 0, number = 0, found = 0, ignore = 0;

--argc; ++argv; // skip program name

while (argc > 0 && (*argv)[0] == '-')
{
while ((c = *++argv[0]))
{
--argc;

switch (c)
{
case 'x':
except = 1;
break;
case 'n':
number = 1;
break;
case 'i':
ignore = 1;
break;
default:
printf("Illegal option\n");
argc = 0;
found = -1;
}
}
}

FILE* fp = stdin;

if (argc > 1 && *argv)
{
fp = fopen(*argv, "r");
++argv;
}

const char* pattern = *argv;

if (fp != NULL && pattern != NULL)
{
char line[MAXLINE] = {0};

while (getLine(line, MAXLINE, fp) > 0) // note getLine() leaves the newline character in the buffer!
{
++lineno;

char oline[MAXLINE] = {0};

if (ignore)
{
copy(oline, line);
strlower(line);
strlower(*argv);
}
if (match(line, pattern))
{
if (number)
{
printf("%ld: ", lineno);
}
if (ignore)
{
printf("%s", oline);
}
else
{
printf("%s\n", line);
}
found++;
}
}
}
else
{
printf("error, cmd line args messed up.\n");
}

return found;
}


P.S. I assume the command line args could work as:


./mgrep file_list .c$

[Arndt]

I have this program:


#include <stdio.h>
#include "useful_functions.h"
#define MAXLINE 1000

int main(int argc, char *argv[]){
char line[MAXLINE];
long lineno = 0;
int c, except = 0, number = 0, found = 0, ignore = 0;

while (--argc > 0 && (*++argv)[0] == '-'){
while (c = *++argv[0]){
switch (c) {
case 'x':
except = 1;
break;
case 'n':
number = 1;
break;
case 'i':
ignore = 1;
break;
default:
printf("Illegal option\n");
argc = 0;
found = -1;
}
}
}
FILE *fp;
*++argv;
fp = fopen(*argv, "r");
*argv--;
if (fp == NULL){
while (getline(line, MAXLINE, stdin) > 0){
lineno++;
char oline[MAXLINE];
if (ignore){
copy(oline, line);
strlower(line);
strlower(*argv);
}
if (match(line, *argv)){
if (number){
printf("%ld: ", lineno);
}
if (ignore){
printf("%s", oline);
}else{
printf("%s", line);
}
found++;
}
}
}else{
while(getline(line,MAXLINE, fp) > 0){
lineno++;
char oline[MAXLINE];
if (ignore){
copy(oline, line);
strlower(line);
strlower(*argv);
}
if (match(line, *argv)){
if (number){
printf("%ld: ", lineno);
}
if (ignore){
printf("%s", oline);
}else{
printf("%s", line);
}
found++;
}
}
}
return found;
}


the functions defined in the header file are:


//strcpy clone
void copy(char to[], char from[]){
int i = 0;
while ((to[i] = from[i]) != '\0'){
++i;
}
}

//tolower clone
char lower(char c){
if (c >= 'A' && c <= 'Z'){
return c + 'a' - 'A';
}else{
return c;
}
}

void strlower(char string[]){
int i;
for(i=0;string[i] != '\0';i++){
string[i] = lower(string[i]);
}
}

int getline(char s[], int lim, FILE *f){
int c, i;
for (i=0; i<lim-1 && (c=getc(f))!=EOF && c!='\n'; ++i){
s[i] = c;
}
if (c == '\n'){
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}

int match(const char *string, char *pattern) {
int status;
regex_t re;
if(regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB) != 0) {
return 0;
}
status = regexec(&re, string, (size_t)0, NULL, 0);
regfree(&re);
if(status != 0) {
return 0;
}
return 1;
}

when run like this:


ls | /.mgrep .c$

I expect it to print out all files that end with '.c', but it prints nothing

For me to be able to compile this, I need to include the file <regex.h> as well.

It's not a good idea to include code (function definitions) in .h files. Put them in a .c file and put the declarations in a .h file.

The cause of the problem is apparent if you put a trace output call in your function 'match'; the strings still end with a newline, so .c$ can never match.

[matmatmat]

It's not a good idea to include code (function definitions) in .h files. Put them in a .c file and put the declarations in a .h file.

Sorry, I had it like this,
.h


void afunction();

.c


void afunction(){
}

[johnl]

Also, if you want to match the literal '.' character you need to escape it:


ls -l . | ./mpgrep "\.c"

[dwhitney67]

Also, if you want to match the literal '.' character you need to escape it:


ls -l . | ./mpgrep "\.c"

Cool, thanks for that tip. I tested the program I submitted earlier, and it works!