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I want to extract a string abc*xyz from a text file.
* indicates arbitrary no. of characters.

I'm only able to do it when the string has definite no. of characters
or the string length is constant: i.e. five or the string is abc?????
xyz
How can i generalize it for any length of the string?

Umesh wrote:
> I want to extract a string abc*xyz from a text file.
> * indicates arbitrary no. of characters.
>
> I'm only able to do it when the string has definite no. of characters
> or the string length is constant: i.e. five or the string is abc?????
> xyz
> How can i generalize it for any length of the string?
>
Have you looked up regular expressions yet?

--
Ian Collins.

"Umesh" <> schrieb im Newsbeitrag
news: ups.com...
>I want to extract a string abc*xyz from a text file.
> * indicates arbitrary no. of characters.
>
> I'm only able to do it when the string has definite no. of characters
> or the string length is constant: i.e. five or the string is abc?????
> xyz
> How can i generalize it for any length of the string?
You may want to look for regex, a librarx for regular expressions.
http://directory.fsf.org/regex.html

Bye, Jojo

Umesh wrote:

> I want to extract a string abc*xyz from a text file.
> * indicates arbitrary no. of characters.
>
> I'm only able to do it when the string has definite no. of characters
> or the string length is constant: i.e. five or the string is abc?????
> xyz
> How can i generalize it for any length of the string?

I don't know how you can generalise it, because I don't
know what your specifically doing.

But, assuming you don't just want to fall back to using
regular expressions, I don't see what your problem is.

Find `abc` (easy-peasy strstr-squeezy). Then find `xyz`
starting from after the `b`. Viola.

Perhaps you haven't described your full problem?

--
Shakespeare Hedgehog
"Based on their behaviour so far -- I have no idea" /Sahara/

"Umesh" <> wrote in message
news: ups.com...
>I want to extract a string abc*xyz from a text file.
> * indicates arbitrary no. of characters.
>
> I'm only able to do it when the string has definite no. of characters
> or the string length is constant: i.e. five or the string is abc?????
> xyz
> How can i generalize it for any length of the string?
>
As others have pointed out, if you want to handle the geneneral problem of
"how can I match a string with charcteristics such and such" you want
regular expressions.
However for a one off simple pattern regular expressions are overkill.

Use strncmp() to compare the first three character to "abc". Call strlen()
to find the end of the string, move back three places (make sure you don't
move into memory you don't own, place minus one), the call strcmp() with
"xyz".

Warp it all up in a little function of its own
--
Free games and programming goodies.
http://www.personal.leeds.ac.uk/~bgy1mm

/* This is what I can do. If the length of the string starting with
abc & ending with xyz is known(11 in this case), I can program it as
follows. But if the length of the string varies between 10 to 50* what
should I do? Thanks. /

//abc?????xyz
#include<stdio.h>
#include<stdlib.h>
int main()
{

FILE *f,*fp;
f=fopen("c:/1.txt","r");
if(f==NULL)
{
puts("Error opening file");
exit(0);
}
fp=fopen("c:/2.txt","w");

char c[12];
while((c[0]=getc(f))!=EOF)
if(c[0]=='a' && (c[1]=getc(f))!=EOF && c[1]=='b' && (c[2]=getc(f))!
=EOF && c[2]=='c'&& (c[3]=getc(f))!=EOF && c[3]!=' ' && (c[4]=getc(f))!
=EOF && c[4]!=' ' && (c[5]=getc(f))!=EOF && c[5]!=' ' &&
(c[6]=getc(f))!=EOF && c[6]!=' ' && (c[7]=getc(f))!=EOF && c[7]!=' '
&& (c[8]=getc(f))!=EOF && c[8]=='x'&& (c[9]=getc(f))!=EOF &&
c[9]=='y' && (c[10]=getc(f))!=EOF && c[10]=='z')
{
c[11]='\0';
fprintf(fp,"%s\n",c);

}
fclose(f);
fclose(fp);
return 0;

}

Umesh wrote:
> /* This is what I can do. If the length of the string starting with
> abc & ending with xyz is known(11 in this case), I can program it as
> follows. But if the length of the string varies between 10 to 50* what
> should I do? Thanks. /
>
1) learn how to post.
2) find a regular expression library.

--
Ian Collins.

"Umesh" <> ha scritto nel messaggio
news: oups.com...
> /* This is what I can do. If the length of the string starting with
> abc & ending with xyz is known(11 in this case), I can program it as
> follows. But if the length of the string varies between 10 to 50* what
> should I do? Thanks. /
No, it doesn't. "abc45678xyz" doesn't work.
You are only comparing the string with "abc xyz".

>
> //abc?????xyz
> #include<stdio.h>
> #include<stdlib.h>
> int main()
> {
>
> FILE *f,*fp;
> f=fopen("c:/1.txt","r");
> if(f==NULL)
> {
> puts("Error opening file");
Write that to stderr, not to stdout...
> exit(0);
Use EXIT_FAILURE, not 0 which means 'success'...
> }
> fp=fopen("c:/2.txt","w");
Check it for NULL, too.
>
> char c[12];
> while((c[0]=getc(f))!=EOF)
EOF doesn't fit in a unsigned char and might compare equal to a
valid signed char.
see www.c-faq.com, question 12.1.

> if(c[0]=='a' && (c[1]=getc(f))!=EOF && c[1]=='b' && (c[2]=getc(f))!
> =EOF && c[2]=='c'&& (c[3]=getc(f))!=EOF && c[3]!=' ' && (c[4]=getc(f))!
> =EOF && c[4]!=' ' && (c[5]=getc(f))!=EOF && c[5]!=' ' &&
> (c[6]=getc(f))!=EOF && c[6]!=' ' && (c[7]=getc(f))!=EOF && c[7]!=' '
> && (c[8]=getc(f))!=EOF && c[8]=='x'&& (c[9]=getc(f))!=EOF &&
> c[9]=='y' && (c[10]=getc(f))!=EOF && c[10]=='z')
What a mess...
What's wrong with
scanf("%11c", c);
if (!strcmp(c, "abc xyz"))...
> {
> c[11]='\0';
> fprintf(fp,"%s\n",c);
>
> }
> fclose(f);
> fclose(fp);
Check wheter these succeeded.
> return 0;
>
> }
>

Try:
/*not compiled, not tested*/
#define MAXLINE 16383
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
int status;
FILE *infp, *outfp;
char buf[MAXLINE+1];
char *str, *endstr = NULL;
infp = fopen("c:/1.txt", "r");
if (infp == NULL) {
perror("Unable to open input file");
exit(EXIT_FAILURE);
}
outfp = fopen("c:/2.txt", "r");
if (outfp == NULL) {
perror("Unable to open or create output file");
fclose(infp);
exit(EXIT_FAILURE);
}
while (fgets(buf, MAXLINE, infp)) {
endstr = NULL;
(str = strstr(buf, "abc")) && (endstr = strstr(str,"xyz"));
if (endstr != NULL)
fprintf(outfp, "%*s", endstr-str+3, str);
}
status = ferror(infp) || ferror(infp);
if (fclose(infp)) {
perror("Unable to close input file");
status++;
}
if (fclose(outfp)) {
perror("Unable to close output file");
status++;
}
return status ? EXIT_FAILURE : 0;
}

"Army1987" <> ha scritto nel messaggio
news:f39663$vqa$...
>
> "Umesh" <> ha scritto nel messaggio
> news: oups.com...
>> /* This is what I can do. If the length of the string starting with
>> abc & ending with xyz is known(11 in this case), I can program it as
>> follows. But if the length of the string varies between 10 to 50* what
>> should I do? Thanks. /
> No, it doesn't. "abc45678xyz" doesn't work.
> You are only comparing the string with "abc xyz".
>
>>
>> //abc?????xyz
>> #include<stdio.h>
>> #include<stdlib.h>
>> int main()
>> {
>>
>> FILE *f,*fp;
>> f=fopen("c:/1.txt","r");
>> if(f==NULL)
>> {
>> puts("Error opening file");
> Write that to stderr, not to stdout...
>> exit(0);
> Use EXIT_FAILURE, not 0 which means 'success'...
>> }
>> fp=fopen("c:/2.txt","w");
> Check it for NULL, too.
>>
>> char c[12];
>> while((c[0]=getc(f))!=EOF)
> EOF doesn't fit in a unsigned char and might compare equal to a
> valid signed char.
> see www.c-faq.com, question 12.1.
>
>> if(c[0]=='a' && (c[1]=getc(f))!=EOF && c[1]=='b' && (c[2]=getc(f))!
>> =EOF && c[2]=='c'&& (c[3]=getc(f))!=EOF && c[3]!=' ' && (c[4]=getc(f))!
>> =EOF && c[4]!=' ' && (c[5]=getc(f))!=EOF && c[5]!=' ' &&
>> (c[6]=getc(f))!=EOF && c[6]!=' ' && (c[7]=getc(f))!=EOF && c[7]!=' '
>> && (c[8]=getc(f))!=EOF && c[8]=='x'&& (c[9]=getc(f))!=EOF &&
>> c[9]=='y' && (c[10]=getc(f))!=EOF && c[10]=='z')
> What a mess...
> What's wrong with
> scanf("%11c", c);
> if (!strcmp(c, "abc xyz"))...
>> {
>> c[11]='\0';
>> fprintf(fp,"%s\n",c);
>>
>> }
>> fclose(f);
>> fclose(fp);
> Check wheter these succeeded.
>> return 0;
>>
>> }
>>
>
> Try:
> /*not compiled, not tested*/
> #define MAXLINE 16383
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> int main(void)
> {
> int status;
> FILE *infp, *outfp;
> char buf[MAXLINE+1];
> char *str, *endstr = NULL;
> infp = fopen("c:/1.txt", "r");
> if (infp == NULL) {
> perror("Unable to open input file");
> exit(EXIT_FAILURE);
> }
> outfp = fopen("c:/2.txt", "r");
> if (outfp == NULL) {
> perror("Unable to open or create output file");
> fclose(infp);
> exit(EXIT_FAILURE);
> }
> while (fgets(buf, MAXLINE, infp)) {
> endstr = NULL;
> (str = strstr(buf, "abc")) && (endstr = strstr(str,"xyz"));
> if (endstr != NULL)
> fprintf(outfp, "%*s", endstr-str+3, str);
fprintf(outfp, "%.*s\n", endstr-str+3, str);
> }
> status = ferror(infp) || ferror(infp);
status = ferror(infp) || ferror(outfp);
> if (fclose(infp)) {
> perror("Unable to close input file");
> status++;
> }
> if (fclose(outfp)) {
> perror("Unable to close output file");
> status++;
> }
> return status ? EXIT_FAILURE : 0;
> }
>

Umesh wrote:
> I want to extract a string abc*xyz from a text file.
> * indicates arbitrary no. of characters.
>
> I'm only able to do it when the string has definite no. of characters
> or the string length is constant: i.e. five or the string is abc?????
> xyz
> How can i generalize it for any length of the string?

Using what the Standard library provides, you can do

const char *the_string = ...;
const char *abc, *xyz;

abc = strstr(the_string, "abc");
if (abc != NULL) {
xyz = strstr(abc + 3, "xyz");
if (xyz != NULL) {
printf ("Found \"%.*s\"\n",
(int)(xyz + 3 - abc), abc);

--
Eric Sosman
lid