Overwrite file snippet with php?

Question

I don’t know how to explain my problem, so I’ll illustrate:

I’m using PHP and would like to manipulate a file . txt of n lines. Each line has a standard size of 20 characters.

For example... the first 8 characters refer to a shipping date (ddmmaaa), the 2 next to the state of origin (SP, RJ, ...), the other 2 to the destination state and the last 8 to the product code.

Linha 1: 01012014RJPA00001472
Linha 2: 03121997MGRS00192010
...
Linha n: 28092012AMAC00000071

What I’d like to know is how to overwrite one of these terms (not the entire line, not the entire file) and save the file.

Type: On line 2 of the file I want to change the source state from MG to MT without changing the other file data. As if I took the pointer to a position before the 'MG' press the keyboard insert and type 'MT'.

Answer 1

It would be interesting if you used regular expressions for this.

You said your text file is composed of lines in the following format:

• 20 characters each
• the first 10 characters are dates, irrelevant to our purposes
• the following 2 characters are the UF, since we want to work
• the following 8 characters are also irrelevant

Therefore, the basic regular expression for each line would be:

/^(?P<data>.*){10}(?P<uf>.*){2}(?P<etc>.*){8}$/

To replace this data, just use the function preg_replace:

$siglaABuscar = 'MT';
$novaSigla    = 'MG';
$arquivo      = file_get_contents('arquivo.txt');
$arquivo      = preg_replace("/^(?P<data>.*){10}(?P<uf>$siglaABuscar){2}(?P<etc>.*){8}$/g", "$1$novaSigla$3", $arquivo);
file_put_contents('arquivo.txt', $arquivo);

PS: I wrote the code from the head, there may be some adjustments to be made.

Answer 2

There are several ways... What you asked for, I believe is basically this:

<?php

// Tamanho padrão da sua linha
$linha_tamanho_default = 20;

// Array que define o inicio do valor na linha de acordo com o tipo de dado
$inicio = array(
    "DATA" => 0,
    "UF" => 8,
    "DESTINO" => 10,
    "CODIGO" => 12,
);

// Define o tamanho de cada item de acordo com o tipo de dado
$tamanho = array(
    "DATA" => 8,
    "UF" => 2,
    "DESTINO" => 2,
    "CODIGO" => 8,
);

// simulando o arquivo em uma string
// equivale a um arquivo txt com o conteudo do comentário abaixo:
/* 
01012014RJPA00001472
03121997MGRS00192010
28092012AMAC00000071
*/
$arquivo = "01012014RJPA00001472\n03121997MGRS00192010\n28092012AMAC00000071";


/***** Abaixo os parâmetros definem que a UF da 3ª linha será substituida por RJ */

// Define que TIPO de valor será substituido
$tipo = "UF";
// Define a linha que será alterada
$linha = 3;
// Define o NOVO valor
$valor = "RJ";

// Calcula a posição para a substituição
// usa $linha-1 (pois a contagem inicia em 0)
// usa $linha_tamanho_default+1 (pois inclui o \n)
// soma com o inicio do item que deseja substituir de acordo com a linha
$posicao = ($linha-1)*($linha_tamanho_default+1) + $inicio[$tipo];

// Retorna o arquivo   
$arquivo = substr_replace($arquivo, $valor, $posicao, $tamanho[$tipo] );

// Printa os resultados
echo $arquivo;

?>

Answer 3

Here are some tips that might help

fopen(), fread(), fgets(), fwrite(), fclose() methods are used to access and change files in your php script. http://br.php.net/manual/en/function.fopen.php

Another option is to "pull everything to an array", make the changes, and then re-write the file. (If there are too many checks and changes, it may be a good option)

$arrayDeLinhas = file($filename, FILE_IGNORE_NEW_LINES);

This will give you an array of the file lines, then you can handle the information as you wish.

Here you can find a method to help you handle the string. http://php.net/manual/en/book.strings.php

I believe wordwrap and substr_replace should help you. But from now on it’s your algorithm organization, so it’s up to you!