DPL Positional Matchers

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• Reference
• Updated on Aug 05, 2026

Positional matchers are zero-width matchers that constrain where a pattern can match within the input. They produce no captured value and must be combined with other matchers such as LD, WORD, or IPADDR.

Positional matchers always refer to the absolute start or end of the input string, regardless of newlines. Use EOL to match line boundaries.

BOS, BOF

BOS (beginning of string) and BOF (beginning of file) match the position at the very start of the input.

Returns

BOS and BOF produce no output. They are positional anchors that constrain matching to the start of the input.

Basic examples

Example 1: Match input that starts with INFO:

Use the following expression to check whether the input starts with INFO::

BOS 'INFO:' LD

See how to use in DQL

data record(input = "INFO: server started"),
     record(input = "DEBUG: handler invoked"),
     record(input = "Log entry - INFO: started")
| fieldsAdd result = matchesPattern(input, "BOS 'INFO:' LD")

Example 2: Parse the header line from a multi-line CSV string

Given the following input:

"name","surname"
"Ned","Flanders"
"Homer","Simpson"
"Charles","Burns"

Use the following expression to extract the first line:

BOS LD:header

See how to use in DQL

data record(input = """"name","surname"
"Ned","Flanders"
"Homer","Simpson"
"Charles","Burns"""")
| parse input, "BOS LD:header"

MOS, MOF

MOS (middle of string) and MOF (middle of file) match any position that is neither the start nor the end of the input. Because parse and matchesPattern work on the input as a whole, MOS is mainly used inside iterative matching with the parseAll function, where it restricts matches to positions other than the very start.

Returns

MOS and MOF produce no output. They are positional anchors that exclude matches at the start or end of the input.

Basic examples

Example 1: Match ERROR in the middle of the input

Use the following expression to check whether ERROR appears in the middle of the input—neither at the start nor at the end:

LD MOS 'ERROR' MOS LD

See how to use in DQL

data record(input = "Got ERROR while parsing"),
     record(input = "ERROR while parsing"),
     record(input = "Failed with ERROR"),
     record(input = "Operation succeeded")
| fieldsAdd result = matchesPattern(input, "LD MOS 'ERROR' MOS LD")

Example 2: Parse all data rows from a multi-line CSV string

Given the following input:

"name","surname"
"Ned","Flanders"
"Homer","Simpson"
"Charles","Burns"

Use the following expression with parseAll to extract every line except the first one. MOS ensures the header line at position 0 is skipped:

MOS DQS:name ',' DQS:surname (EOL | EOS)

See how to use in DQL

data record(input = """"name","surname"
"Ned","Flanders"
"Homer","Simpson"
"Charles","Burns"""")
| fields rows = parseAll(input, "MOS DQS:name ',' DQS:surname (EOL | EOS)")

EOS, EOF

EOS (end of string) and EOF (end of file) match the position at the very end of the input. Use EOS with parse to require the matched portion to extend to the input's last character—without EOS, parse succeeds even when extra content follows the match. In matchesPattern, end-anchoring is implicit, so EOS is most useful with parse or inside alternations.

Returns

EOS and EOF produce no output. They are positional anchors that constrain matching to the end of the input.

Basic examples

Example 1: Match input that ends with OK

Use the following expression to check whether the input ends with OK:

LD 'OK' EOS

See how to use in DQL

data record(input = "Status: OK"),
     record(input = "Status: failed"),
     record(input = "OK then failed")
| fieldsAdd result = matchesPattern(input, "LD 'OK' EOS")

Example 2: Match an IP address at the end of the record

Use the following expression to check whether each record ends with an IP address. The expression matches only when no content follows the IP:

LD IPADDR EOS

See how to use in DQL

data record(input = "userId=1246 ip=124.5.2.4"),
     record(input = "userId=441122 ip=75.52.12.1 status=error message='Login failed'"),
     record(input = "userId=753434 ip=4.4.3.2")
| fieldsAdd result = matchesPattern(input, "LD IPADDR EOS")

Example 3: Parse an IP address with and without EOS

Given the following input, which contains two IP addresses:

Log has 127.0.0.1 and ends with 156.34.11.23

LD IP:out

data record(input = "Log has 127.0.0.1 and ends with 156.34.11.23")
| parse input, "LD IP:out"

LD (IP:out EOS)

data record(input = "Log has 127.0.0.1 and ends with 156.34.11.23")
| parse input, "LD (IP:out EOS)"