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    <pre><code> while ( !feof( readPtr ) ) { if ( client.acctNum != 0 ) { </code></pre> <p>At this point in the code, you haven't <em>read</em> anything. Nothing. :)</p> <p>You've opened the file, you've checked to see if you've reached the end of the file, but there's no code yet to read anything from the file, so your <code>if</code> condition is just checking against the initialized structure at the start.</p> <p>Looping over input typically works best if the input is read at the <em>top</em> of the loop. (There are exceptions, but this doesn't look like one of them.)</p> <p>Try this as a starting point for your loop:</p> <pre><code>while(fread(&amp;client, sizeof(struct clientData), 1, filePtr)) { if (client.acctNum) { client.balance -= charge; fseek(filePtr, - sizeof(struct clientData), SEEK_CUR); if (1 != fwrite(&amp;client, sizeof(struct clientData), 1, filePtr)) perror("Error writing to file"); } } </code></pre> <p>The error handling can probably be improved; maybe the whole edit should be aborted. (Mandatory record locking on the file could have <em>some</em> writes fail and some writes succeed, but that is pretty unlikely.)</p> <p><strong>Update</strong></p> <p>Your <code>fseek()</code> call is basing the new file position based on multiplying the account number by the size of the <code>struct clientData</code>. This works ONLY IF your records are sorted, no numbers are skipped, and it starts at <code>0</code> and works up. (Your example input file is not sorted; you even have a record with a <code>0</code> account number in the middle of 'valid' records.) So switch to <code>fseek(..., SEEK_CUR)</code> instead.</p>
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    1. POupdate random access file in c
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    1. COI hope we learned an important lesson about cobbling together questions based on cut-n-paste :) I found another issue, post updated shortly.
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    2. CO@user695752, two approaches: **1** to continue using `(client.acctNum - 1)` in your `fseek(3)`: (a) you must be _certain_ that your records are in sorted numerical order, starting at `1` and you cannot skip any numbers in the input file. (b) you must use `SEEK_SET`. **2** Or you can use `SEEK_CUR` without any `client.acctNum` scaling, and just back up over the _one_ record you just read.
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