grepros 1.3.0
grep for ROS bag files and live topics: read, filter, export
License: BSD
Requires Python: >=2.7
Keywords: ROS ROS1 ROS2 rosbag grep

grepros
=======

grep for ROS bag files and live topics: read, filter, export.

Searches through ROS messages and matches any message field value by regular
expression patterns or plain text, regardless of field type.
Can also look for specific values in specific message fields only.

By default, matches are printed to console. Additionally, matches can be written
to a bagfile or HTML/CSV/MCAP/Parquet/Postgres/SQL/SQLite, or published to live topics.

Supports both ROS1 and ROS2. ROS environment variables need to be set, at least `ROS_VERSION`.

Supported bag formats: `.bag` (ROS1), `.db3` (ROS2), `.mcap` (ROS1, ROS2).

In ROS1, messages can be grepped even if Python packages for message types are not installed.
Using ROS1 live topics requires ROS master to be running.

Using ROS2 requires Python packages for message types to be available in path.

Supports loading custom plugins, mainly for additional output formats.

Usable as a Python library, see doc/LIBRARY.md.
Full API documentation available at https://suurjaak.github.io/grepros.

[![Screenshot](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/th_screen.png)](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/screen.png)


- Example usage
- Installation
- Inputs
- Outputs
- Matching and filtering
- Plugins
- Notes on ROS1 vs ROS2
- All command-line arguments
- Dependencies
- Attribution
- License


Example usage
-------------

Search for "my text" in all bags under current directory and subdirectories:

    grepros -r "my text"

Print 30 lines of the first message from each live ROS topic:

    grepros --max-per-topic 1 --lines-per-message 30 --live

Find first message containing "future" (case-sensitive) in my.bag:

    grepros future -I --max-count 1 --name my.bag

Find 10 messages, from geometry_msgs package, in "map" frame,
from bags in current directory, reindexing any unindexed bags:

    grepros frame_id=map --type geometry_msgs/* --max-count 10 --reindex-if-unindexed

Pipe all diagnostics messages with "CPU usage" from live ROS topics to my.bag:

    grepros "CPU usage" --type *DiagnosticArray --no-console-output --write my.bag

Find messages with field "key" containing "0xA002",
in topics ending with "diagnostics", in bags under "/tmp":

    grepros key=0xA002 --topic *diagnostics --path /tmp

Find diagnostics_msgs messages in bags in current directory,
containing "navigation" in fields "name" or "message",
print only header stamp and values:

    grepros --type diagnostic_msgs/* --select-field name message \
            --emit-field header.stamp status.values -- navigation

Print first message from each lidar topic on ROS1 host 1.2.3.4, without highlight:

    ROS_MASTER_URI=http://1.2.3.4::11311 \
    grepros --live --topic *lidar* --max-per-topic 1 --no-highlight

Export all bag messages to SQLite and Postgres, print only export progress:

    grepros -n my.bag --write my.bag.sqlite --no-console-output --no-verbose --progress

    grepros -n my.bag --write postgresql://user@host/dbname \
            --no-console-output --no-verbose --progress


Patterns use Python regular expression syntax, message matches if all match.
'*' wildcards use simple globbing as zero or more characters,
target matches if any value matches.

Note that some expressions may need to be quoted to avoid shell auto-unescaping
or auto-expanding them, e.g. `linear.x=2.?5` should be given as `"linear.x=2\.?5"`.

Care must also be taken with unquoted wildcards, as they will auto-expanded by shell
if they happen to match paths on disk.


Installation
------------

grepros is written in Python, supporting both Python 2 and Python 3.

Developed and tested under ROS1 Noetic and ROS2 Foxy,
works in later ROS2 versions (Galactic, Humble, Iron, Jazzy, Kilted, and likewise Rolling);
also works in the earlier ROS1 version Melodic (lacking MCAP and Parquet support).


### Using pip

    pip install grepros

This will add the `grepros` command to path.

Requires ROS Python packages
(ROS1: rospy, roslib, rosbag, genpy;
 ROS2: rclpy, rosidl_parser, rosidl_runtime_py, builtin_interfaces).

For ROS1, if only using bag files and no live topics, minimal ROS1 Python
packages can also be installed separately with:

    pip install rospy rosbag roslib roslz4 \
    --extra-index-url https://rospypi.github.io/simple/


### Using apt

If ROS apt repository has been added to system:

    sudo apt install ros-noetic-grepros  # ROS1 Noetic

    sudo apt install ros-foxy-grepros    # ROS2 Foxy

This will add the `grepros` command to the global ROS1 / ROS2 environment.


### Using catkin

In a ROS1 workspace, under the source directory:

    git clone https://github.com/suurjaak/grepros.git
    cd grepros
    catkin build --this

This will add the `grepros` command to the local ROS1 workspace path.


### Using colcon

In a ROS2 workspace, at the workspace root:

    git clone https://github.com/suurjaak/grepros.git src/grepros
    colcon build --packages-select grepros

This will add the `grepros` command to the local ROS2 workspace path.


Inputs
------

Input is either from one or more ROS bag files (default), or from live ROS topics.

### bag

Read messages from ROS bag files, by default all in current directory.

For reading bags in MCAP format, see the doc/DETAIL.md#mcap.

Recurse into subdirectories when looking for bagfiles:

    -r
    --recursive

Read specific filenames (supports * wildcards):

    --n        /tmp/*.bag
    --filename my.bag 2021-11-*.bag

Scan specific paths instead of current directory (supports * wildcards):

    -p     /home/bags/2021-11-*
    --path my/dir

Emit messages on original bag timeline from first matched message,
optionally with a speedup or slowdown factor:

    --time-scale       # At original rate
    --time-scale 2     # Twice faster
    --time-scale 0.5   # Twice slower

Reindex unindexed ROS1 bags before processing
(note: creates backup copies of files, into same directory as file):

    --reindex-if-unindexed
    --reindex-if-unindexed --progress

Decompress archived ROS bags before processing
(`.zst` `.zstd` extensions, requires `zstandard` Python package)
(note: unpacks archived file to disk, into same directory as file):

    --decompress
    --decompress --progress

Order bag messages first by topic or type, and only then by time:

    --order-bag-by topic
    --order-bag-by type


### live

    --live

Read messages from live ROS topics instead of bagfiles.

Requires `ROS_MASTER_URI` and `ROS_ROOT` to be set in environment if ROS1.

Set custom queue size for subscribing (default 10):

    --queue-size-in 100

Use ROS time instead of system time for incoming message timestamps:

    --ros-time-in


Outputs
-------

There can be any number of outputs: printing to console (default),
publishing to live ROS topics, or writing to file or database.

### console

Default output is to console, in ANSI colors, mimicking `grep` output.

Disable printing messages to console:

    --no-console-output

Manage color output:

    --color always  (default)
    --color auto    (auto-detect terminal support)
    --color never   (disable colors)

Note that when paging color output with `more` or `less`, the pager needs to
accept raw control characters (`more -f` or `less -R`).


### bag

    --write path/to/my.bag [format=bag] [overwrite=true|false]
            [rollover-size=NUM] [rollover-count=NUM] [rollover-duration=NUM]
            [rollover-template=STR]

Write messages to a ROS bag file, the custom `.bag` format in ROS1,
or the `.db3` SQLite database format in ROS2. If the bagfile already exists,
it is appended to, unless specified to overwrite.

Specifying `format=bag` is not required
if the filename ends with `.bag` in ROS1 or `.db3` in ROS2.

For writing bags in MCAP format, see the doc/DETAIL.md#mcap.

More on doc/DETAIL.md#rollover.


### live

    --publish

Publish messages to live ROS topics. Topic prefix and suffix can be changed,
or topic name set to one specific name:

    --publish-prefix  /myroot
    --publish-suffix  /myend
    --publish-fixname /my/singular/name

One of the above arguments needs to be specified if publishing to live ROS topics
while grepping from live ROS topics, to avoid endless loops.

Set custom queue size for publishers (default 10):

    --queue-size-out 100


### csv

    --write path/to/my.csv [format=csv] [overwrite=true|false]

Write messages to CSV files, each topic to a separate file, named
`path/to/my.full__topic__name.csv` for `/full/topic/name`.


### html

    --write path/to/my.html [format=html] [overwrite=true|false]
            [template=/path/to/html.template]
            [rollover-size=NUM] [rollover-count=NUM] [rollover-duration=NUM]
            [rollover-template=STR]

Write messages to an HTML file, with a linked table of contents,
message timeline, message type definitions, and a topically traversable message list.

[![Screenshot](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/th_screen_html.png)](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/screen_html.png)

More on doc/DETAIL.md#rollover.


### postgres

    --write postgresql://username@host/dbname [format=postgres]
            [commit-interval=NUM] [nesting=array|all]
            [dialect-file=path/to/dialects.yaml]

Write messages to a Postgres database, with tables `pkg/MsgType` for each ROS message type,
and views `/full/topic/name` for each topic.

[![Screenshot](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/th_screen_postgres.png)](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/screen_postgres.png)


### sqlite

    --write path/to/my.sqlite [format=sqlite] [overwrite=true|false]
            [commit-interval=NUM] [message-yaml=true|false] [nesting=array|all]
            [dialect-file=path/to/dialects.yaml]
            [rollover-size=NUM] [rollover-count=NUM] [rollover-duration=NUM]
            [rollover-template=STR]

Write an SQLite database with tables `pkg/MsgType` for each ROS message type
and nested type, and views `/full/topic/name` for each topic.

[![Screenshot](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/th_screen_sqlite.png)](https://raw.githubusercontent.com/suurjaak/grepros/gh-pages/img/screen_sqlite.png)

More on outputs in doc/DETAIL.md#outputs.


### console / html message formatting

Set maximum number of lines to output per message:

    --lines-per-message 5

Set maximum number of lines to output per message field:

    --lines-per-field 2

Start message output from, or stop output at, message line number:

    --start-line  2   # (1-based if positive
    --end-line   -2   # (count back from total if negative)

Output only the fields where patterns find a match:

    --matched-fields-only

Output only matched fields and specified number of lines around match:

    --lines-around-match 5

Output only specific message fields (supports nested.paths and * wildcards):

    --emit-field *data

Skip outputting specific message fields (supports nested.paths and * wildcards):

    --no-emit-field header.stamp

Wrap matches in custom texts:

    --match-wrapper @@@
    --match-wrapper "<<<<" ">>>>"

Set custom width for wrapping message YAML printed to console (auto-detected from terminal by default):

    --wrap-width 120


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 reading 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 "<topic /robot/enabled>.data"

    # (Match if at least 10 messages have been encountered in /robot/alerts)
    --condition "len(<topic /robot/alerts>) > 10"

    # (Match if last two messages in /robot/mode have equal .value)
    --condition "<topic /robot/mode>[-2].value == <topic /robot/mode>[-1].value"

    # (Match while control is enabled and robot is moving straight and level)
    --condition "<topic */control_enable>.data and <topic */cmd_vel>.linear.x > 0 " \
                "and <topic */cmd_vel>.angular.z < 0.02"


Condition namespace:

| Name                         | Description
| ---------------------------- | ---------------------------------------------------------------
|                              |
| `msg`                        | current message from data source
| `topic`                      | full name of current message topic
| `<topic /my/topic>`          | topic by full name or * wildcard
| `len(<topic ..>)`            | number of messages encountered in topic
| `bool(<topic ..>)`           | whether any message encountered in topic
| `<topic ..>.xyz`             | attribute `xyz` of last message in topic
| `<topic ..>[index]`          | topic message at position
|                              | (from first encountered if index >= 0, last encountered if < 0)
| `<topic ..>[index].xyz`      | attribute `xyz` of topic message at position
| |
| `value in msg`               | whether any field in current message contains value
| `value in <topic ..>`        | whether any field in last topic message contains value
| `value in <topic ..>[index]` | whether any field in topic message at position contains value


Condition is automatically false if trying to access attributes of a message not yet received.


Plugins
-------

    --plugin some.python.module some.other.module.Class

Load one or more Python modules or classes as plugins.

Specifying `--plugin someplugin` and `--help` will include plugin options in printed help.

Built-in plugins:

### embag

    --plugin grepros.plugins.embag

Use the [embag](https://github.com/embarktrucks/embag) library for reading ROS1 bags.

Significantly faster, but library tends to be unstable.


### mcap

    --plugin grepros.plugins.mcap

Read or write messages in [MCAP](https://mcap.dev) format.


### parquet

    --plugin grepros.plugins.parquet \
    --write path/to/my.parquet [format=parquet] [overwrite=true|false] \
            [column-name=rostype:value] [type-rostype=arrowtype] \
            [idgenerator=callable] [nesting=array|all] [writer-argname=argvalue]

Write messages to Apache Parquet files (columnar storage format, version 2.6),
each message type to a separate file.


### sql

    --plugin grepros.plugins.sql \
    --write path/to/my.sql [format=sql] [overwrite=true|false] \
            [nesting=array|all] [dialect=clickhouse|postgres|sqlite] \
            [dialect-file=path/to/dialects.yaml]

Write SQL schema to output file, CREATE TABLE for each message type
and CREATE VIEW for each topic.

More on plugins in doc/DETAIL.md#plugins.


Notes on ROS1 vs ROS2
---------------------

In ROS1, message type packages do not need to be installed locally to be able to
read messages from bags or live topics, as bags and topic publishers provide
message type definition texts, and message classes can be generated at run-time
from the type definition text. This is what rosbag does automatically,
and so does grepros.

Additionally, each ROS1 message type has a hash code computed from its type
definition text, available both in live topic metadata, and bag metadata.
The message type definition hash code allows to recognize changes
in message type packages and use the correct version of the message type.

ROS2 does not provide message type definitions, neither in the .db3 bagfiles
nor in live topics. Due to this, the message type packages always need to be
installed. Also, ROS2 does not provide options for generating type classes
at run-time, and it does not have the concept of a message type hash.

These are serious limitations in ROS2 compared to ROS1, at least with versions
up to ROS2 Humble and counting, and require extra work to smooth over.
Without knowing which version of a message type package a bag was recorded with,
reading bag messages with changed definitions can result in undefined behaviour.

If the serialized message structure happens to match (e.g. a change swapped
the order of two `int32` fields), messages will probably be deserialized
seemingly successfully but with invalid content. If the serialized structure
does not match, the result is a run-time error.

Because of this, it is prudent to always include a snapshot archive of used
message type packages, when recording ROS2 bags.

grepros does provide the message type hash itself in ROS2 exports, by calculating
the ROS2 message type hash on its own from the locally installed type definition.

The situation in ROS2 with the newer MCAP format is a bit better: at least
parsed message data can be read from MCAP bags without needing the specific message
packages installed. However, reading from MCAP bags yields only data structs,
not usable as ROS messages e.g. for publishing to live topics.
grepros tries to smooth over this difference by defaulting to locally installed
message classes if available, with definitions matching message types in bag.


All command-line arguments
--------------------------

```
positional arguments:
  PATTERN               pattern(s) to find in message field values,
                        all messages match if not given,
                        can specify message field as NAME=PATTERN
                        (supports nested.paths and * wildcards)

optional arguments:
  -h, --help            show this help message and exit
  -F, --fixed-strings   PATTERNs are ordinary strings, not regular expressions
  -I, --no-ignore-case  use case-sensitive matching in PATTERNs
  -v, --invert-match    select messages not matching PATTERNs
  -e, --expression      PATTERNs are a logical expression
                        like 'this AND (this2 OR NOT "skip this")',
                        with elements as patterns to find in message fields
  --version             display version information and exit
  --live                read messages from live ROS topics instead of bagfiles
  --publish             publish matched messages to live ROS topics
  --write TARGET [format=bag|csv|html|mcap|parquet|postgres|sql|sqlite] [KEY=VALUE ...]
                        write matched messages to specified output,
                        format is autodetected from TARGET if not specified.
                        Bag or database will be appended to if it already exists.
                        Keyword arguments are given to output writer.
                          column-NAME=ROSTYPE:VALUE
                                                   additional column to add in Parquet output,
                                                   like column-bag_hash=string:26dfba2c
                          commit-interval=NUM      transaction size for Postgres/SQLite output
                                                   (default 1000, 0 is autocommit)
                          dialect-file=path/to/dialects.yaml
                                                   load additional SQL dialect options
                                                   for Postgres/SQL/SQLite output
                                                   from a YAML or JSON file
                          dialect=clickhouse|postgres|sqlite
                                                   use specified SQL dialect in SQL output
                                                   (default "sqlite")
                          idgenerator=CALLABLE     callable or iterable for producing message IDs 
                                                   in Parquet output, like 'uuid.uuid4' or 'itertools.count()';
                                                   nesting uses UUID values by default
                          message-yaml=true|false  whether to populate table field messages.yaml
                                                   in SQLite output (default true)
                          nesting=array|all        create tables for nested message types
                                                   in Parquet/Postgres/SQL/SQLite output,
                                                   only for arrays if "array" 
                                                   else for any nested types
                                                   (array fields in parent will be populated 
                                                    with foreign keys instead of messages as JSON)
                          overwrite=true|false     overwrite existing file
                                                   in bag/CSV/HTML/MCAP/Parquet/SQL/SQLite output
                                                   instead of appending to if bag or database
                                                   or appending unique counter to file name
                                                   (default false)
                          rollover-count=NUM       message limit for individual files
                                                   in bag/HTML/MCAP/SQLite output
                                                   (supports abbreviations like 1K or 2M or 3G)
                          rollover-duration=INTERVAL
                                                   message time span limit for individual files
                                                   in bag/HTML/MCAP/SQLite output
                                                   as seconds (supports abbreviations like 60m or 2h or 1d)
                          rollover-size=NUM        size limit for individual files
                                                   in bag/HTML/MCAP/SQLite output
                                                   as bytes (supports abbreviations like 1K or 2M or 3G)
                          rollover-template=STR    output filename template for individual files
                                                   in bag/HTML/MCAP/SQLite output,
                                                   supporting strftime format codes like "%H-%M-%S"
                                                   and "%(index)s" as output file index
                          template=/my/path.tpl    custom template to use for HTML output
                          type-ROSTYPE=ARROWTYPE   custom mapping between ROS and pyarrow type
                                                   for Parquet output, like type-time="timestamp('ns')"
                                                   or type-uint8[]="list(uint8())"
                          writer-ARGNAME=ARGVALUE  additional arguments for Parquet output
                                                   given to pyarrow.parquet.ParquetWriter
  --plugin PLUGIN [PLUGIN ...]
                        load a Python module or class as plugin
                        (built-in plugins: grepros.plugins.embag, 
                         grepros.plugins.mcap, grepros.plugins.parquet, 
                         grepros.plugins.sql)
  --stop-on-error       stop further execution on any error like unknown message type

Filtering:
  -t TOPIC [TOPIC ...], --topic TOPIC [TOPIC ...]
                        ROS topics to read if not all (supports * wildcards)
  -nt TOPIC [TOPIC ...], --no-topic TOPIC [TOPIC ...]
                        ROS topics to skip (supports * wildcards)
  -d TYPE [TYPE ...], --type TYPE [TYPE ...]
                        ROS message types to read if not all (supports * wildcards)
  -nd TYPE [TYPE ...], --no-type TYPE [TYPE ...]
                        ROS message types to skip (supports * wildcards)
  --condition CONDITION [CONDITION ...]
                        extra conditions to require for matching messages,
                        as ordinary Python expressions, can refer to last messages
                        in topics as <topic /my/topic>; topic name can contain wildcards.
                        E.g. --condition "<topic /robot/enabled>.data" matches
                        messages only while last message in '/robot/enabled' has data=true.
  -t0 TIME, --start-time TIME
                        earliest timestamp of messages to read
                        as relative seconds if signed,
                        or epoch timestamp or ISO datetime
                        (for bag input, relative to bag start time
                        if positive or end time if negative,
                        for live input relative to system time,
                        datetime may be partial like 2021-10-14T12)
  -t1 TIME, --end-time TIME
                        latest timestamp of messages to read
                        as relative seconds if signed,
                        or epoch timestamp or ISO datetime
                        (for bag input, relative to bag start time
                        if positive or end time if negative,
                        for live input relative to system time,
                        datetime may be partial like 2021-10-14T12)
  -n0 INDEX, --start-index INDEX
                        message index within topic to start from
                        (1-based if positive, counts back from bag total if negative)
  -n1 INDEX, --end-index INDEX
                        message index within topic to stop at
                        (1-based if positive, counts back from bag total if negative)
  --every-nth-message NUM
                        read every Nth message within topic, starting from first
  --every-nth-interval SECONDS
                        read messages at least N seconds apart within topic
  --every-nth-match NUM
                        emit every Nth match in topic, starting from first
  -sf FIELD [FIELD ...], --select-field FIELD [FIELD ...]
                        message fields to use in matching if not all
                        (supports nested.paths and * wildcards)
  -ns FIELD [FIELD ...], --no-select-field FIELD [FIELD ...]
                        message fields to skip in matching
                        (supports nested.paths and * wildcards)
  -m NUM, --max-count NUM
                        number of matched messages to emit (per each file if bag input)
  --max-per-topic NUM   number of matched messages to emit from each topic
                        (per each file if bag input)
  --max-topics NUM      number of topics to emit matches from (per each file if bag input)
  --unique-only         only emit matches that are unique in topic,
                        taking --select-field and --no-select-field into account
                        (per each file if bag input)

Output control:
  -B NUM, --before-context NUM
                        emit NUM messages of leading context before match
  -A NUM, --after-context NUM
                        emit NUM messages of trailing context after match
  -C NUM, --context NUM
                        emit NUM messages of leading and trailing context
                        around match
  -ef FIELD [FIELD ...], --emit-field FIELD [FIELD ...]
                        message fields to emit in console/CSV/HTML/Parquet output if not all
                        (supports nested.paths and * wildcards)
  -nf FIELD [FIELD ...], --no-emit-field FIELD [FIELD ...]
                        message fields to skip in console/CSV/HTML/Parquet output
                        (supports nested.paths and * wildcards)
  -mo, --matched-fields-only
                        emit only the fields where PATTERNs find a match in console/HTML output
  -la NUM, --lines-around-match NUM
                        emit only matched fields and NUM message lines
                        around match in console/HTML output
  -lf NUM, --lines-per-field NUM
                        maximum number of lines to emit per field in console/HTML output
  -l0 NUM, --start-line NUM
                        message line number to start emitting from in console/HTML output
                        (1-based if positive, counts back from total if negative)
  -l1 NUM, --end-line NUM
                        message line number to stop emitting at in console/HTML output
                        (1-based if positive, counts back from total if negative)
  -lm NUM, --lines-per-message NUM
                        maximum number of lines to emit per message in console/HTML output
  --match-wrapper [STR [STR ...]]
                        string to wrap around matched values in console/HTML output,
                        both sides if one value, start and end if more than one,
                        or no wrapping if zero values
                        (default "**" in colorless output)
  --wrap-width NUM      character width to wrap message YAML console output at,
                        0 disables (defaults to detected terminal width)
  --color {auto,always,never}
                        use color output in console (default "always")
  --no-meta             do not print source and message metainfo to console
  --no-filename         do not print bag filename prefix on each console message line
  --no-highlight        do not highlight matched values
  --no-console-output   do not print matches to console
  --progress            show progress bar when not printing matches to console
  --verbose             print status messages during console output
                        for publishing and writing, and error stacktraces
  --no-verbose          do not print status messages during console output
                        for publishing and writing

Bag input control:
  -n FILE [FILE ...], --filename FILE [FILE ...]
                        names of ROS bagfiles to read if not all in directory
                        (supports * wildcards)
  -p PATH [PATH ...], --path PATH [PATH ...]
                        paths to scan if not current directory
                        (supports * wildcards)
  -r, --recursive       recurse into subdirectories when looking for bagfiles
  --order-bag-by {topic,type}
                        order bag messages by topic or type first and then by time
  --decompress          decompress archived bagfiles with recognized extensions (.zst .zstd)
  --reindex-if-unindexed
                        reindex unindexed bagfiles (ROS1 only), makes backup copies
  --time-scale [FACTOR]
                        emit messages on original bag timeline from first matched message,
                        optionally with a speedup or slowdown factor

Live topic control:
  --publish-prefix PREFIX
                        prefix to prepend to input topic name on publishing match
  --publish-suffix SUFFIX
                        suffix to append to input topic name on publishing match
  --publish-fixname TOPIC
                        single output topic name to publish all matches to,
                        overrides prefix and suffix
  --queue-size-in SIZE  live ROS topic subscriber queue size (default 10)
  --queue-size-out SIZE
                        output publisher queue size (default 10)
  --ros-time-in         use ROS time instead of system time for incoming message
                        timestamps from subsribed live ROS topics
```


Dependencies
------------

grepros requires Python 3.8+ or Python 2.7,
and the following 3rd-party Python packages:

- pyyaml (https://pypi.org/project/PyYAML)
- six (https://pypi.org/project/six)
- ROS1: rospy, roslib, rosbag, genpy
- ROS2: rclpy, rosidl_parser, rosidl_runtime_py, builtin_interfaces

Optional, for decompressing archived bags:

- zstandard (https://pypi.org/project/zstandard)

Optional, for faster reading of ROS1 bags:

- embag (https://github.com/embarktrucks/embag)

Optional, for Postgres output:

- psycopg2 (https://pypi.org/project/psycopg2)

Optional, for Parquet output:

- pandas (https://pypi.org/project/pandas)
- pyarrow (https://pypi.org/project/pyarrow)

Optional, for MCAP input-output:

- mcap (https://pypi.org/project/mcap)
- mcap_ros1_support (https://pypi.org/project/mcap_ros1_support)
- mcap_ros2_support (https://pypi.org/project/mcap_ros2_support)

Optional, for generating API documentation:

- doxypypy (https://pypi.org/project/doxypypy;
            needs latest master: `pip install git+https://github.com/Feneric/doxypypy`)

All dependencies other than rospy/rclpy can be installed with:

    pip install pyyaml six zstandard embag psycopg2 pandas pyarrow \
                mcap mcap_ros1_support mcap_ros2_support \
                git+https://github.com/Feneric/doxypypy


Attribution
-----------

Includes a modified version of step, Simple Template Engine for Python,
(c) 2012, Daniele Mazzocchio, https://github.com/dotpy/step,
released under the MIT license.


License
-------

Copyright (c) 2021 by Erki Suurjaak.
Released as free open source software under the BSD License,
see LICENSE.md for full details.