Example:
void stringEvaluation(char *name){
if (strstr(name, "Tall") != NULL)
--here I would like to print only "John Doe"--
}
int main{
char name[160 + 1];
scanf("%[^\n]%*c", name);
stringEvaluation(name);
return 0;
}
and this is the input
"John Doe (45). Black. Tall. Brown eyes"
Your request is unclear. For example, do as follows.
#include <stdio.h>
#include <string.h>
#include <ctype.h>
void stringEvaluation(const char *s){
const char *p;
if(s == NULL || *s == '\0'){
puts("invalid format.");
return ;
}
(p = strchr(s, '(')) || (p = strchr(s, '.'));
if(p == NULL){
puts("invalid format.");
return ;
}
//find end
while(!isalpha((unsigned char)p[-1]))
--p;
while(s < p)
putchar(*s++);
}
int main(void){
char name[160 + 1] = "";
scanf("%160[^\n]%*c", name);
stringEvaluation(name);
return 0;
}
I am using strtok() to get the name. Please note, this will work only if you have "()" in your string.
void stringEvaluation(char *name){
if (strstr(name, "Tall") != NULL)
{
char *nameEnd = strtok(name, "("); //Returns address of '('
if(NULL != nameEnd)
{
int nameLength = nameEnd - name - 1; // 1 for space after name.
char *onlyName = malloc((nameLength + 1) * sizeof(char)); // 1 for terminating '\0'
if(NULL != onlyName)
{
//Copy name part.
strncpy(onlyName, name, nameLength);
onlyName[nameLength] = '\0'; //Make onlyName a string
printf("Name: [%s]\n", onlyName);
free(onlyName);
onlyName = NULL;
}
}
}
}
I have assumed that name will be at first place in your input string. Then following small logic will work for you.
void stringEvaluation(char *name){
char *p;
char OutPut[50]={0};
if (strstr(name, "Tall") != NULL)
{
p = strstr(name," ");
p++;
p = strstr(p," ");
strncpy(OutPut,name,(p-name));
printf("name=%s\n",OutPut);
}
}
Related
#include <stdio.h>
#include <string.h>
int main()
{
char buf[50] = "user/local/etc/bin/example.txt";
char* ptr;
ptr = strchr(buf, '/');
char path[20];
strncpy(path, buf, ptr-buf);
path[ptr-buf] =0;
printf("%s\n", path);
return 0;
}
I am able the get the substring before the first occurence of '/' i.e. I can get user but how can I get the substring after the second occurrence of '/' i.e. local and also the last occurence of '/' i.e. example without the extension .txt? How can it be done efficiently
I wouldn't use strchr for this. The problem is that strchr can only find one specific character but you care about both / and . Instead I would iterate the string using a pointer and check for both characters inside the loop..
Something like:
int main()
{
char buf[50] = "user/local/etc/bin/example.txt";
char* pStart = buf;
char* pCurrent = buf;
while(*pCurrent != '\0')
{
if (*pCurrent == '/' || *pCurrent == '.')
{
char str[20] = {0};
strncpy(str, pStart, pCurrent - pStart);
printf("%s\n", str);
pStart = pCurrent+1;
}
++pCurrent;
}
return 0;
}
Output:
user
local
etc
bin
example
If you really want to do this using strchr it could be like:
int main()
{
char buf[50] = "user/local/etc/bin/example.txt";
char* pStart = buf;
char* pCurrent = strchr(pStart, '/');
while(pCurrent != NULL)
{
char str[20] = {0};
strncpy(str, pStart, pCurrent - pStart);
printf("%s\n", str);
pStart = pCurrent+1;
pCurrent = strchr(pStart, '/');
}
pCurrent = strchr(pStart, '.');
if (pCurrent != NULL)
{
char str[20] = {0};
strncpy(str, pStart, pCurrent - pStart);
printf("%s\n", str);
}
return 0;
}
but as you can see, it requires a bit more code than the first example.
Use strtok() in this case For detailed description check this link ! Hope this helps!
Use this:
#include <stdio.h>
#include <string.h>
#define MAXLEN 100
int main(void)
{
char buf[] = "user/local/etc/bin/example.txt";
char substring[MAXLEN+1];
char *a, *b;
int len;
b = buf;
while ( (a = strchr(b, '/')) != NULL || (a = strchr(b, '.')) != NULL)
{
len = a - b;
if (len > MAXLEN)
return 0;
memcpy(substring, b, len);
substring[len] = 0;
printf("'%s'\n", substring);
b = a + 1;
}
return 0;
}
Here is the ouput:
'user'
'local'
'etc'
'bin'
'example'
I am parsing a file in C, line by line. Here is an exemple of what I am trying to do :
I have a line for example :
word word word WORDTOFIND: word1 word2 word word
What I want to do is : When I find the word WORDTOFIND, get the two next words (word1 and word2 in this case) of the line. Is there an easy way to do that in C ? I know about the strstr function, but I don't find a way to get the next two words word1 and word2 after I found the good one.
One approach would be this:
int main(void)
{
char *str = "rated rat cat bat hat";
char *key = "rat ";
char *pointer = NULL;
char nwords = 2;
if ((pointer = strstr(str, key)) != NULL)
{
while (*pointer != ' ') pointer++;
while (nwords >= 0)
{
printf("%c", *pointer);
if (*pointer == ' ') {
nwords--;
} else if (*pointer == '\0') {
exit(0);
}
pointer++;
}
}
}
You can try an aproach like this, using strtok to parse the words at every space. This code also uses malloc and realloc to allocate space for an array of strings, and grows it when needed.
The code looks like this:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAXCHAR 100
void exit_if_null(void *ptr, const char *msg);
char *stripped_word(char *word);
int
main(int argc, char const *argv[]) {
FILE *filename;
char line[MAXCHAR];
char *word, *newword;
char **allwords;
int init_size = 8, count = 0, i;
const char *key = "WORDTOFIND";
filename = fopen("files.txt", "r");
if (filename == NULL) {
fprintf(stderr, "%s\n", "Error reading file!");
exit(EXIT_FAILURE);
}
allwords = malloc(init_size * sizeof(*allwords));
exit_if_null(allwords, "Initial Allocation");
while (fgets(line, MAXCHAR, filename) != NULL) {
word = strtok(line, " \n");
while (word != NULL) {
if (count == init_size) {
init_size *= 2;
allwords = realloc(allwords, init_size * sizeof(*allwords));
}
allwords[count] = malloc(strlen(word)+1);
exit_if_null(allwords[count], "Initial Allocation");
newword = stripped_word(word);
strcpy(allwords[count], newword);
count++;
word = strtok(NULL, " \n");
free(newword);
}
}
for (i = 0; i < count; i++) {
if (strcmp(key, allwords[i]) == 0) {
printf("Next two words:\n");
printf("%s\n", allwords[i+1]);
printf("%s\n", allwords[i+2]);
}
free(allwords[i]);
allwords[i] = NULL;
}
free(allwords);
allwords = NULL;
return 0;
}
void
exit_if_null(void *ptr, const char *msg) {
if (!ptr) {
printf("Unexpected null pointer: %s\n", msg);
exit(EXIT_FAILURE);
}
}
char
*stripped_word(char *word) {
int i, pos = 0;
char *result;
result = malloc(strlen(word)+1);
exit_if_null(result, "Initial Allocation");
for (i = 0; word[i] != '\0'; i++) {
if (isalpha(word[i]) || isdigit(word[i])) {
result[pos++] = word[i];
}
}
result[pos] = '\0';
return result;
}
I'm trying to write a code that goes through a given string using a pointer to parse it.
The original code I wrote worked fine but it was... redundant so I tried making it into a function call to make it more concise. Here is what i have:
char inputArray[300];
char buffer[300];
char username[100];
char password[100];
char name[100];
int i=0;
void repeat(char *to)
{
while(*to!='=')
{
to++;
}
}
void array(char *mm,char *tt)
{
i=0;
while(*tt!='+')
{
mm[i]=*tt;
tt++;
i++;
}
}
int main()
{
printf("give me the shit in this fashion: username=?+password=?+real=?\n");
scanf("%s",inputArray);
strcpy(buffer,inputArray);
char *tok=buffer;
repeat(tok);
tok++;
array(username,tok);
repeat(tok);
tok++;
array(password,tok);
tok++;
repeat(tok);
tok++;
array(name,tok);
}
For some reason it won't give me back the pointer array tok where it left off from the previous function call. why is that? it acts as if after calling it the pointer starts back from the beginning.
Functions receive copies of their arguments. Original arguments remain unaffected.
Giving something back has a special syntax in C: the return statement. Thus
char* repeat (char *to) // <- this function gives back a char*
{
while (*to != '=')
{
to++;
}
return to; // <- giving something back
}
Call it like this:
tok = repeat(tok);
Treat array in the same fashion.
Note 1, this function will result in *undefined behaviour if the string doesn't contain '='.
Note 2, it is also possible to pass a pointer to tok as the other answer suggests, but for sake of clarity it is only recommended to use this style when you need to return more than one thing from a function.
just change your repeat to this:
void repeat(char **to) {
while (**to != '=') {
(*to)++;
}
}
and call it like this:
repeat(&tok);
and always check for errors:
if (scanf("%299s", inputArray) != 1){
printf("incorrect input\n");
return 1;
}
and your sample code (and add check for errors in array and repeat to not go out of bounds):
#include <inttypes.h>
#include <stdio.h>
#include <stdint.h>
char inputArray[300];
char buffer[300];
char username[300];
char password[300];
char name[300];
int i = 0;
void repeat(char **to) {
while (**to != '=') {
(*to)++;
}
}
void array(char *mm, char *tt){
i = 0;
while (*tt != '+') {
mm[i] = *tt;
tt++;
i++;
}
}
int main() {
printf("give me the shit in this fashion: username=?+password=?+real=?\n");
if (scanf("%299s", inputArray) != 1){
printf("incorrect input\n");
return 1;
}
inputArray[299] = 0;
strcpy(buffer, inputArray);
char *tok = buffer;
repeat(&tok);
tok++;
array(username, tok);
repeat(&tok);
tok++;
array(password, tok);
tok++;
repeat(&tok);
tok++;
array(name, tok);
}
and you may use this to not go out of bounds:
#include <inttypes.h>
#include <stdio.h>
#include <stdint.h>
char* read_str(char *src, char *dst){
char *p, *q;
p = src;
while (*p != 0 && *p != '=') p++;
if (*p == 0) {
*dst = 0;
return NULL; // '=' not found
}
p++;
q = p;
while (*q != 0 && *q != '+') q++;
//if (*q == 0) return NULL;// '+' not found
while (p <= q) *dst++ = *p++;
dst--;
*dst = 0;
q++;
return q;
}
#define MAX_LEN 100
int main() {
char username[MAX_LEN];
char password[MAX_LEN];
char name[MAX_LEN];
char inputArray[MAX_LEN] = "username=Alex+password=123+real=Alex";
char *p = inputArray;
p = read_str(p, username);
if (p == NULL)return 1; // error
p = read_str(p, password);
if (p == NULL)return 1; // error
read_str(p, name);
printf("username: %s \n", username);
printf("password: %s \n", password);
printf(" name: %s \n", name);
}
Just a quick one: in C I have a buffer full of data like below:
char buffer[255]="CODE=12345-MODE-12453-CODE1-12355"
My question is how to search through this. For example for the CODE=12345, section bear in mind that the numbers change, so I would like to search like this CODE=***** using wildcard or preset amount of spaces after the CODE= part.
This method wont compile last one left to try
#include <stdio.h>
#include <string.h>
#include <windows.h>
int main ()
{
char buf[255]="CODE=12345-MODE-12453-CODE1-12355";
#define TRIMSPACES(p) while(*p != '\0' && isspace((unsigned char)*p) != 0) ++p
#define NSTRIP(p, n) p += n
#define STRIP(p) ++p
char* getcode(const char *input)
{
char *p = (char*) input, *buf, *pbuf;
if((buf = malloc(256)) == NULL)
return NULL;
pbuf = buf;
while(*p != '\0') {
if(strncmp(p, "CODE", 3) == 0) {
NSTRIP(p, 4); //remove 'code'
TRIMSPACES(p);//trim white-space after 'code'
if(*p != '=')
return NULL;
STRIP(p); // remove '='
TRIMSPACES(p); //trim white-spaces after '='
/* copy the value until found a '-'
note: you must be control the size of it,
for avoid overflow. we allocated size, that's 256
or do subsequent calls to realloc()
*/
while(*p != '\0' && *p != '-')
*pbuf ++ = *p++;
// break;
}
p ++;
}
//put 0-terminator.
*pbuf ++ = '\0';
return buf;
}
//
}
You could use the sscanf() function:
int number;
sscanf(buffer, "CODE = %i", &number);
for that to work well your buffer has to be null terminated.
Another way to do it instead of sscanf():
char *input, *code;
input = strstr(buf, "CODE");
if(input == NULL) {
printf("Not found CODE=\n");
return -1;
}
code = strtok(strdup(input), "=");
if(code != NULL) {
code = strtok(NULL, "-");
printf("%s\n", code); // code = atoi(code);
} else {
//not found '='
}
Or more robust way.. a bit more complex:
#define TRIMSPACES(p) while(*p != '\0' && isspace((unsigned char)*p) != 0) ++p
#define NSTRIP(p, n) p += n
#define STRIP(p) ++p
char* getcode(const char *input, size_t limit)
{
char *p = (char*) input, *buf, *pbuf;
size_t i = 0;
while(*p != '\0') {
if(strncmp(p, "CODE", 3) == 0) {
NSTRIP(p, 4); //remove 'code'
TRIMSPACES(p);//trim all white-spaces after 'code'
/* check we have a '=' after CODE (without spaces).
if there is not, returns NULL
*/
if(*p != '=')
return NULL;
/* ok. We have.. now we don't need of it
just remove it from we output string.
*/
STRIP(p);
/* remove again all white-spaces after '=' */
TRIMSPACES(p);
/* the rest of string is not valid,
because are white-spaces values.
*/
if(*p == '\0')
return NULL;
/* allocate space for store the value
between code= and -.
this limit is set into second parameter.
*/
if((buf = malloc(limit)) == NULL)
return NULL;
/* copy the value until found a '-'
note: you must be control the size of it,
for don't overflow. we allocated 256 bytes.
if the string is greater it, do implementation with
subjecents call to realloc()
*/
pbuf = buf;
while(*p != '\0' && *p != '-' && i < limit) {
*pbuf ++ = *p++;
i ++;
}
*pbuf ++ = '\0';
return buf;
}
p ++;
}
return NULL;
}
And then:
char buf[255] = "foo baa CODE = 12345-MODE-12453-CODE-12355";
char *code = getcode(buf,256);
if(code != NULL) {
printf("code = %s\n", code);
free(code);
} else {
printf("Not found code.\n");
}
output:
code = 12345
Check out this online.
if you want to don't differentiate case, you can use the strncasecmp() that's POSIX function.
Assuming the CODE= part always comes at the beginning of the string, it's pretty easy:
sscanf(buffer, "CODE = %d", &number);
...but you want buffer to be char[255], not unsigned long.
Edit: If the CODE= part isn't necessarily at the beginning of the string, you can use strstr to find CODE in the buffer, do your sscanf starting from that point, then look immediately following that:
int codes[256];
char *pos = buffer;
size_t current = 0;
while ((pos=strstr(pos, "CODE")) != NULL) {
if (sscanf(pos, "CODE = %d", codes+current))
++current;
pos += 4;
}
Edit2:
For example, you'd use this something like this:
#include <stdio.h>
#include <string.h>
#include <windows.h>
int main ()
{
// This is full of other junk as well
char buffer[255]="CODE=12345 MODE-12453 CODE=12355" ;
int i;
int codes[256];
char *pos = buffer;
size_t current = 0;
while ((pos=strstr(pos, "CODE")) != NULL) {
if (sscanf(pos, "CODE = %d", codes+current))
++current;
pos += 4;
}
for (i=0; i<current; i++)
printf("%d\n", codes[i]);
return 0;
}
For me, this produces the following output:
12345
12355
...correctly reading the two "CODE=xxx" sections, but skipings over the "MODE=yyy" section.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *getcode(const char *str, const char *pattern){
//pattern: char is match, space is skip, * is collect
static const char *p=NULL;
char *retbuf, *pat;
int i, match, skip, patlen;
if(str != NULL) p=str;
if(p==NULL || *p=='\0') return NULL;
if(NULL==(retbuf=(char*)malloc((strlen(p)+1)*sizeof(char))))
return NULL;
pat = (char*)pattern;
patlen = strlen(pat);
i = match = skip = 0;
while(*p){
if(isspace(*p)){
++p;
++skip;
continue;
}
if(*pat){
if(*p == *pat){
++match;
++p;
++pat;
} else if(*pat == '*'){
++match;
retbuf[i++]=*p++;
++pat;
} else {
if(match){//reset
pat=(char*)pattern;
p -= match + skip -1;
i = match = skip = 0;
} else //next
++p;
}
} else {
break;
}
}
if(i){//has match
retbuf[i++]='\0';
retbuf=realloc(retbuf, i);
return retbuf;
} else {
free(retbuf);
return NULL;
}
}
int main (){
char *code;
code=getcode("CODE=12345-MODE-12453-CODE1-12355", "CODE=*****");
printf("\"%s\"\n",code);//"12345"
free(code);
code=getcode(" CODE = 12345-MODE-12453-CODE1-12355", "CODE=*****");
printf("\"%s\"\n",code);//"12345"
free(code);
code=getcode("CODE-12345-MODE-12453-CODE1-12355", "CODE=*****");
if(code==NULL)printf("not match\n");//not match
code=getcode("CODE=12345-MODE-12453-CODE=12355", "CODE=*****");
printf("\"%s\"\n",code);//"12345"
free(code);
code=getcode(NULL, "CODE=*****");
printf("\"%s\"\n",code);//"12355"
free(code);
code=getcode("CODE=12345-MODE-12453-CODE1-12355", "CODE=*****");
printf("\"%s\"\n",code);//"12345"
free(code);
code=getcode(NULL, "CODE1-*****");
printf("\"%s\"\n",code);//"12355"
free(code);
return 0;
}
I have a structure
typedef struct store
{
char name[11];
int age;
} store;
and a main function(below is part of it):
int main()
{
int i=0;
int inputs;
char line[100];
char name[11];
char command[11];
store read[3000];
while(i < 3000 && gets(line) != NULL)
{
int tempage;
inputs = sscanf(line, "%10s %10s %d", command, name, &tempage);
if (inputs == 3)
{
if (strcmp(command, "register") == 0)
{
strncpy(read[i].name, name,10);
read[i].age = tempage;
i++;
....
I need to modify it so that it can read a line of arbitrary length, and store the name from the line which is also a string of arbitrary length using malloc and realloc.
How should I approach this?
What you need to do is read the line in smaller increments, and resize your buffer as you go.
As an example (not tested and not meaning to be particularly elegant, just an example):
char *readline(FILE *f)
{
char *buf = NULL;
size_t bufsz = 0, len = 0;
int keep_going = 1;
while (keep_going)
{
int c = fgetc(f);
if (c == EOF || c == '\n')
{
c = 0; // we'll add zero terminator
keep_going = 0; // and terminate the loop afterwards
}
if (bufsz == len)
{
// time to resize the buffer.
//
void *newbuf = NULL;
if (!buf)
{
bufsz = 512; // some arbitrary starting size.
newbuf = malloc(bufsz);
}
else
{
bufsz *= 2; // issue - ideally you'd check for overflow here.
newbuf = realloc(buf, bufsz);
}
if (!newbuf)
{
// Allocation failure. Free old buffer (if any) and bail.
//
free(buf);
buf = NULL;
break;
}
buf = newbuf;
}
buf[len++] = c;
}
return buf;
}
Change the name[11] to *name;
Allocate memory for that everytime using malloc.
By the way, register is a keyword in C language. You can't use it like you did !
I think what you're looking for is:
char* name;
name = (char*)malloc(sizeof(char));
This alternative approach is similar to #asveikau's, but economize on the use of malloc() by copying on the stack.
Please do not use this for homework answer.
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
char * slurponeline(FILE *f, int s) {
const int size = 4096;
char buffer[size];
char * r;
int c,i=0;
while( i<size && (c = fgetc(f),c>=0 && c!='\n')) buffer[i++]=c;
if (0 == s && 0 == i) return 0;
r = (size==i)? slurponeline(f,s+size):malloc(s+i);
memcpy(r+s,buffer,i);
return r;
}
int main(int argc, char ** argv) {
FILE * f = fopen(argc>1?argv[1]:"a.out","rb");
char * a,*command,*commandend,*name,*nameend;
int age;
while (a = slurponeline(f,0)) {
char * p = a;
while (*p && *p == ' ') ++p; // skip blanks.
command = p;
while (*p && *p != ' ') ++p; // skip non-blanks.
commandend = p;
while (*p && *p == ' ') ++p; // skip blanks.
name = p;
while (*p && *p != ' ') ++p; // skip non-blanks.
nameend = p;
while (*p && *p == ' ') ++p; // skip blanks.
age = atoi(p);
*commandend=0;
*nameend=0;
printf("command: %s, name: %s, age: %d\n",command,name,age);
free(a);
}
}