(RESOLVED) - SD-CARD find a string on text file

Using Arduino Programming Questions
#1

Hello everyone!
Sorry for my newbie question, but I’m trying to find a string on a text file stored on a SD-Card.
I’m using the Arduino Ethernet Shield with SD-Card Slot!

Here is the code created by David A. Mellis and modified by Tom Igoe (SD card read/write)

/*
  SD card read/write
 
 This example shows how to read and write data to and from an SD card file 	
 The circuit:
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4
 
 created   Nov 2010
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe
 
 This example code is in the public domain.
 	 
 */
 
#include <SD.h>

File myFile;
char buf[8];

void setup()
{
 // Open serial communications and wait for port to open:
  Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }


  Serial.print("Initializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin 
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output 
  // or the SD library functions will not work. 
   pinMode(10, OUTPUT);
   
  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");  
    
  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");
    
    // read from the file until there's nothing else in it:
    
    while (myFile.available()) {
        myFile.read(buf,8);        
        if(strncmp(&buf[0],"18429880",8)==0)
        {
            Serial.println("Match!");       
        }
    }
    // close the file:
    myFile.close();
  } else {
  	// if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void loop()
{
	// nothing happens after setup
}

The text file should be like this format:

18429874
18429875
18429876
18429877
18429878
18429879
18429880
18429881
18429882
18429883
18429884
18429885
18429886
18429887

Thanks!
Rodrigo.

#2

You assume the string to match is aligned on an 8-byte boundary, which it won’t be if there are newlines…

#3

Hello MarkT, actually I would like to know if there's a way to find the string on .txt file (I'll use the txt file as a small Database). Thanks, Rodrigo.

#4

actually I would like to know if there's a way to find the string on .txt file

You are doing fine, except that you are not skipping the carriage return and line feed that are between each set of characters that look like a number to you.

Change your code so that you read 10 characters, instead.

You also need to append a NULL to buf after each read, since buf is NOT a string, and strncmp() expects a string.

Don't forget to make buf bigger, to handle the two extra characters AND the NULL.

By the way buf and &buf[0] point to the same memory location, so your strncmp() call could be simpler:

        if(strncmp(buf, "18429880", 8) == 0)
#5

Hi PaulS,

Thank you very much! I just perform a test with a file with more than 15.000 lines and works fine! I just change the buf:

char buf[10];

and:

       myFile.read(buf,10);       
        if(strncmp(buf, "18438846", 8) == 0)
        {
            Serial.println("Match!");
           break;     
        }

Thank you!

#6

hello, trying to use this same method and code to find a string in a text file but when i do it, i only get to the Serial.println(“mydata.txt:”); line.

string search.JPG

#7

hello, trying to use this same method and code to find a string in a text file

I'm certain that the fine folks at http://snippets-r-us.com will be able to help you.

#8

Thank you PaulS, code works now there we extra spaces between numbers in the text file. Is there a way to search for a string in a text file then delete it?

#9

Is there a way to search for a string in a text file

You can read the data from the text file, storing it in a string (NULL terminated array of char), and then determine if that string contains the string of interest.

Deleting it is a bit trickier.You'd need to read the data from one file, and then write it, or a modified version of it, to another file.

#10

ok thanks, trying to use a php in web page to edit the text file but it seems to can't access the text file when served up from the arduino

#11

ok thanks, trying to use a php in web page to edit the text file

How? The PHP engine runs before the page is displayed in the browser. It runs on the server. If the Arduino is the server, how are you running the PHP engine on the Arduino?

What you claim to be doing doesn't make sense.

#12

i am in the research process, i am new to arduino and web design. What i need to do is edit the textfile stored on the arduino ethernet sheild SD card remotely over a local network.

#13

What i need to do is edit the textfile stored on the arduino ethernet sheild SD card remotely over a local network.

Sorry. This still doesn't make sense. The only way for the client to know what is in the text file is for the Arduino-as-server to send the client the contents of the file. In which case, the client MIGHT send back a request to remove some data from the file.

At which point, the Arduino-as-server has no more role, and the Arduino-as-file-owner takes over and modifies the file. PHP has NOTHING to do with editing the file.

Try again.

#14

well thats what i was asking about at first..... if there is a way to remove a specific string from a text file with an arduino function call from a webpage. My plan B is to edit copy of the text file on a remote server then upload it to the arduino each time it is saved.

#15

if there is a way to remove a specific string from a text file with an arduino function call from a webpage.

You can’t call an Arduino function from a webpage.

I think you need to put the Arduino away for a while, and learn about client/server architecture, and getting a client to make a server do something, using a PC as web server. When you understand that, you’ll understand that your questions don’t make sense.

#16

Hi everyone :slight_smile:

Right now what i’m trying to do is make a simple database to .CSV in SDcard…
now, i’m still learning how to write and read on CSV file.
So I tried some example on SDcard that read some data on files

/*
  SD card read/write

 This example shows how to read and write data to and from an SD card file
 The circuit:
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4

 created   Nov 2010
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe

 This example code is in the public domain.

 */

#include <SPI.h>
#include <SD.h>

File myFile;

void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }


  Serial.print("Initializing SD card...");
  // On the Ethernet Shield, CS is pin 4. It's set as an output by default.
  // Note that even if it's not used as the CS pin, the hardware SS pin
  // (10 on most Arduino boards, 53 on the Mega) must be left as an output
  // or the SD library functions will not work.
  pinMode(10, OUTPUT);

  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  myFile = SD.open("test.txt", FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
    // close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }

  // re-open the file for reading:
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");

    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void loop()
{
  // nothing happens after setup
}

but how i can make modification to the code, so that i can read these data and make something cool…
(example)
[ID] [Name]
[1] [James]
[2] [Rudy]

So lets say if i receive data ‘2’ from serial, arduino will open the somerandom.CSV file and will search for id number 2, and says that “Hello Rudy”

Sorry if i’m madly beginner to arduino and C language…
Please give me some support
Thanks ! :slight_smile:

#17

Hey orthho, I am Working on same kind of project. Can You share your progress here!

I am unable to figure-out,.. How to connect php to arduino.

#18

Hello,

Is there a way to search for a string in a text file

@MarlonVets did you manage to find the solution for this. I am facing the same problem with the strings.

#19