Parse structured file (FIX 4.4) in powershell

Question

I need to parse a structured file (FIX protocol 4.4) in powershell. The structure is like this

20220606-21:10:21.930 : 8=FIX.4.49=209 35=W34=35 49=FIXDIRECT.FT 52=20220606-21:10:21.925 56=MM_EUR_FIX_QS 55=US30 262=96 268=2 269=0 270=32921.6 271=2000000 299=16ynjsz-16ynjsz5qCaA 269=1 270=32931.4 271=2000000 299=16ynjsz-16ynjsz5qCaA 10=048

I need to pick only specific values following tags. I need the first value (timestamp) until the colon which does not have a tag number but then need to pick values following specific tag numbers. For example tag values 55, 270 and 271 (multiple 270 and 271 values exist here)

I am able to parse utilizing a simple ordered method of " " and "=" as delimiters

$contents = Get-Content FIX.log
foreach($line in $contents) {
    $s = $line.split("= ")
    write-host $s[0] $s[17] $s[25] $s[27] $s[33] $s[35]
}

however I prefer to be able to pinpoint the value using the tag numbers as there are some lines in the file that do not conform to the same content.

Result should be something like this

20220606-21:10:21.930 US30 32921.6 2000000 32931.4 2000000

Answer 1

Combine -split, -match, and -replace as follows:

• Note: The sample data below, in line with the FIX protocol, uses the SOH control character (code point 0x1) to separate the fields.

# The separator char (SOH) used by the FIX protocol / file format.
$sep = [char] 0x1

# Sample line that simulates your Get-Content call.
$content = "20220606-21:10:21.930${sep}:${sep}8=FIX.4.49=209${sep}35=W34=35${sep}49=FIXDIRECT.FT${sep}52=20220606-21:10:21.925${sep}56=MM_EUR_FIX_QS${sep}55=US30${sep}262=96${sep}268=2${sep}269=0${sep}270=32921.6${sep}271=2000000${sep}299=16ynjsz-16ynjsz5qCaA${sep}269=1${sep}270=32931.4${sep}271=2000000${sep}299=16ynjsz-16ynjsz5qCaA 10=048"

foreach ($line in $content) {

  # Split into fields
  $first, [array] $rest = $line -split $sep

  # Extract the tokens of interest:
  #  * Use the first one as-is
  #  * Among the remaining ones, use -match to filter in only
  #    those with the tag numbers of interest, then use -replace
  #    on the results to strip the tag number plus the separator ("=")
  #    from each.
  $tokensOfInterest =
    , $first + (($rest -match '^(?:55|270|271)=') -replace '^.+=')

  # Output the resulting array as a single-line, space-delimited
  # list, which is how Write-Host stringifies arrays.
  # Note: Do NOT use Write-Host to output *data*.
  Write-Host $tokensOfInterest

}

This yields the sample output in your question, namely:

20220606-21:10:21.930 US30 32921.6 2000000 32931.4 2000000