grepros

Matching and filtering

Any number of patterns can be specified, message matches if all patterns find a match.
If no patterns are given, any message matches.

Match messages containing all of the words:

cpu memory speed

Match messages where frame_id contains "world":

frame_id=world

Match messages where header.frame_id is present:

header.frame_id=.*

Match as plaintext, not Python regular expression patterns:

-F
--fixed-strings

Select non-matching messages instead:

-v
--invert-match

Use case-sensitive matching in patterns (default is insensitive):

-I
--no-ignore-case

Give pattern as a logical expression like this AND (this2 OR NOT "skip this"), with elements as patterns to find in message fields:

-e
--expression

# (Match live messages containing 'cpu' or 'memory')
cpu OR memory --expression --live

Limits

Stop after matching a specified number of messages (per each file if bag input):

-m          100
--max-count 100

Read only a specified number of topics (per each file if bag input):

--max-topics 10

Emit a specified number of matches per topic (per each file if bag input):

--max-per-topic 20

Emit every Nth match in topic, starting from first:

--every-nth-match 10  # (emits matches #1 #11 #21 ..)

Filtering

Read specific topics only (supports * wildcards):

-t      *lidar* *ins*
--topic /robot/sensors/*

Skip specific topics (supports * wildcards):

-nt        *lidar* *ins*
--no-topic /robot/sensors/*

Read specific message types only (supports * wildcards):

-d     *Twist*
--type sensor_msgs/*

Skip specific message types from reading (supports * wildcards):

-nd       *Twist*
--no-type sensor_msgs/*

Set specific message fields to scan (supports nested.paths and * wildcards):

-sf            twist.linear
--select-field *data

Skip specific message fields in scan (supports nested.paths and * wildcards):

-ns               twist.linear
--no-select-field *data

Only emit matches that are unique in topic,
taking --select-field and --no-select-field into account (per each file if bag input):

--unique-only

Start reading from a specific timestamp:

-t0          2021-11     # (using partial ISO datetime)
--start-time 1636900000  # (using UNIX timestamp)
--start-time +100        # (seconds from bag start time, or from script startup time if live input)
--start-time -100        # (seconds from bag end time, or script startup time if live input)

Stop readng at a specific timestamp:

-t1        2021-11     # (using partial ISO datetime)
--end-time 1636900000  # (using UNIX timestamp)
--end-time +100        # (seconds from bag start time, or from script startup time if live input)
--end-time -100        # (seconds from bag end time, or from script startup time if live input)

Start reading from a specific message index in topic:

-n0           -100  # (counts back from topic total message count in bag)
--start-index   10  # (1-based index)

Stop reading at a specific message index in topic:

-n1         -100  # (counts back from topic total message count in bag)
--end-index   10  # (1-based index)

Read every Nth message in topic, starting from first:

--every-nth-message 10  # (reads messages #1 #11 #21 ..)

Read messages in topic with timestamps at least N seconds apart:

--every-nth-interval 5  # (samples topic messages no more often than every 5 seconds)

Conditions

--condition "PYTHON EXPRESSION"

Specify one or more Python expressions that must evaluate as true to search encountered messages. Expressions can access topics, by name or * wildcard, and refer to message fields directly.

# (Match while last message in '/robot/enabled' has data=true)
--condition ".data"

# (Match if at least 10 messages have been encountered in /robot/alerts)
--condition "len() > 10"

# (Match if last two messages in /robot/mode have equal .value)
--condition "[-2].value == [-1].value"

# (Match while control is enabled and robot is moving straight and level)
--condition ".data and .linear.x > 0 and .angular.z < 0.02"