Increment Numbers in an Unknown Substring by One

Question

I need to get the name of the last file that was copied and then increment by one to get the next file. The files follow the pattern DDMM###.TXT where ### will start with 000 and end with 005 for the day. I know I can use substring to get the ###, and then increment by 1, and then used replace to replace the ### with the new incremented "string". I was just wondering if there was a more elegant way to do this.

    $value = $filetotransfer.substring(4,3)
    $newvalue = ([int]$value+1).ToString('000')
    $filetotransfer = $filetotransfer.Replace($value,$newvalue)

Where $filetotransfer can be mmdd000.txt to mmdd005.txt depending on the time of the day.

mklement0 · Answer 1 · 2022-08-04T20:37:53.403

If you're using PowerShell (Core) 7+:

# -> '0506001.txt'
'0506000.txt' -replace '(?<=^\d{4})...', { '{0:000}' -f (1 + $_.Value) }

In Windows PowerShell, the -replace operator doesn't support script blocks ({ ... }) as the replacement operand, which makes the solution more complex, because a direct call to the underlying .NET API is required:
```
# -> '0506001.txt'
[regex]::Replace('0506000.txt', '(?<=^\d{4})...', { param($m) '{0:000}' -f (1 + $m.Value) })
```

For an explanation of these techniques, see this answer.

Increment Numbers in an Unknown Substring by One

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