cw

The best way to tail AWS CloudWatch Logs from your terminal.

Author - Luca Grulla - https://www.lucagrulla.com

• Features
• Installation
• Commands and options
• Examples
• AWS credentials and configuration
• Miscellaneous
• Release notes

Features

• No external dependencies
  • cw is a native executable targeting your OS. No pip, npm, rubygems.
• Fast.
  • cw is written in golang and compiled against your architecture.
• Flexible date and time parser.
  • Work with either Local timezone or UTC (default).
  • Flexible parsing.
    • Human friendly formats, i.e. 2d1h20m to indicate 2 days, 1 hour and 20 minutes ago.
    • a specific hour, i.e. 13:10 to indicate 13:10 of today.
    • a full timestamp 2018-10-20T8:53.
• Multi log groups tailing
  • tail multiple log groups in parallel: cw tail my-auth-service my-web.
• Powerful built-in grep (--grep) and grepv (--grepv).
• JMESPath support for JSON queries (matching the AWS CLI --query flag)
• Pipe operator supported
  • echo my-group | cw tail and cat groups.txt | cw tail.
• Redirection operator >> supported
  • cw tail -f my-stream >> myfile.txt.
• Coloured output
  • --no-color flag to disable if needed.
• Flexible credentials control.
  • By default the AWS .aws/credentials and .aws/profile files are used. Overrides can be achieved with the --profile and --region flags.

Installation

Mac OSX

using Homebrew

brew tap lucagrulla/tap
brew install cw

Linux

using Linuxbrew

brew tap lucagrulla/tap
brew install cw

.deb/.rpm

Download the .deb or .rpm from the releases page and install with dpkg -i and rpm -i respectively.

using Snapcraft.io

Note: If you upgrade to 3.3.0 please note the new alias command. This is required to comply with snapcraft new release rules.

snap install cw-sh
sudo snap connect cw-sh:dot-aws-config-credentials
sudo snap alias cw-sh.cw cw

cw runs with strict confinement; the dot-aws-config-credentials interface connection is required to have access to .aws/config and .aws/credentials files

On Windows

using Scoop.sh

scoop bucket add cw https://github.com/lucagrulla/cw-scoop-bucket.git
scoop install cw

Go tools

go get github.com/lucagrulla/cw

Commands and options

Global flags

• --profile=profile-name Override the AWS profile used for connection.
• --region=aws-region Override the target AWS region.
• --no-color Disable coloured output.
• --endpoint The target AWS endpoint url. By default cw will use the default aws endpoints.
• --no-version-check Ignore checks if a newer version of the module is available.

Commands

• cw ls list all the log groups/log streams within a group

  Usage: cw ls <command>
  
  show an entity
  
  Flags:
    -h, --help               Show context-sensitive help.
        --endpoint=URL       The target AWS endpoint url. By default cw will use the default aws endpoints. NOTE: v4.0.0
                            dropped the flag short version.
        --profile=PROFILE    The target AWS profile. By default cw will use the default profile defined in the
                            .aws/credentials file. NOTE: v4.0.0 dropped the flag short version.
        --region=REGION      The target AWS region. By default cw will use the default region defined in the
                            .aws/credentials file. NOTE: v4.0.0 dropped the flag short version.
        --no-color           Disable coloured output.NOTE: v4.0.0 dropped the flag short version.
        --version            Print version information and quit
        --no-version-check   Ignore checks if a newer version of the module is available.
  
  Commands:
    ls groups
      Show all groups.
  
    ls streams <group>
      Show all streams in a given log group.
  
  cw: error: expected one of "groups",  "streams"

• cw tail tail a given log group/log stream

  Usage: cw tail <groupName[:logStreamPrefix]> ...
  
  Tail log groups/streams.
  
  Arguments:
    <groupName[:logStreamPrefix]> ...    The log group and stream name, with group:prefix syntax. Stream name can be just the prefix. If no stream name is specified all stream names in the given
                                        group will be tailed. Multiple group/stream tuple can be passed. e.g. cw tail group1:prefix1 group2:prefix2 group3:prefix3.
  
  Flags:
    -h, --help                           Show context-sensitive help.
        --endpoint=URL                   The target AWS endpoint url. By default cw will use the default aws endpoints. NOTE: v4.0.0 dropped the flag short version.
        --profile=PROFILE                The target AWS profile. By default cw will use the default profile defined in the .aws/credentials file. NOTE: v4.0.0 dropped the flag short version.
        --region=REGION                  The target AWS region. By default cw will use the default region defined in the .aws/credentials file. NOTE: v4.0.0 dropped the flag short version.
        --no-color                       Disable coloured output.NOTE: v4.0.0 dropped the flag short version.
        --version                        Print version information and quit
        --no-version-check               Ignore checks if a newer version of the module is available.
  
    -f, --follow                         Don't stop when the end of streams is reached, but rather wait for additional data to be appended.
    -t, --timestamp                      Print the event timestamp.
    -i, --event-id                       Print the event Id.
    -s, --stream-name                    Print the log stream name this event belongs to.
    -n, --group-name                     Print the log group name this event belongs to.
    -r, --retry                          Keep trying to open a log group/log stream if it is inaccessible.
    -b, --start="2021-04-11T08:21:52"    The UTC start time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of days, hours and minutes prior to
                                        the present. Denote days with 'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h. If just time is used (format: hh[:mm]) it is expanded to
                                        today at the given time. Full available date/time format: 2017-02-27[T09[:00[:00]].
    -e, --end=STRING                     The UTC end time. Passed as either date/time or human-friendly format. The human-friendly format accepts the number of days, hours and minutes prior to the
                                        present. Denote days with 'd', hours with 'h' and minutes with 'm' i.e. 80m, 4h30m, 2d4h. If just time is used (format: hh[:mm]) it is expanded to today at
                                        the given time. Full available date/time format: 2017-02-27[T09[:00[:00]].
    -l, --local                          Treat date and time in Local timezone.
    -g, --grep=STRING                    Pattern to filter logs by. See http://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/FilterAndPatternSyntax.html for syntax.
    -v, --grepv=STRING                   Equivalent of grep --invert-match. Invert match pattern to filter logs by.
    -q, --query=STRING                   Equivalent of the --query flag in AWS CLI. Takes a JMESPath expression to filter JSON logs by. If the query fails (e.g. the log message was not JSON) then the original line is returned.

Examples

• list of the available log groups

  • cw ls groups

• list of the log streams in a given log group

  • cw ls streams my-log-group

• tail and follow given log groups/streams

  • cw tail -f my-log-group
  • cw tail -f my-log-group:my-log-stream-prefix
  • cw tail -f my-log-group:my-log-stream-prefix my-log-group2
  • cw tail -f my-log-group:my-log-stream-prefix -b2017-01-01T08:10:10 -e2017-01-01T08:05:00
  • cw tail -f my-log-group:my-log-stream-prefix -b7d to start from 7 days ago.
  • cw tail -f my-log-group:my-log-stream-prefix -b3h to start from 3 hours ago.
  • cw tail -f my-log-group:my-log-stream-prefix -b100m to start from 100 minutes ago.
  • cw tail -f my-log-group:my-log-stream-prefix -b2h30m to start from 2 hours and 30 minutes ago.
  • cw tail -f my-log-group -b9:00 -e9:01

• query JSON logs using JMESPath syntax

  • cw tail -f my-log-group --query "machines[?state=='running'].name"

Time and Dates

Time and dates are treated as UTC by default. Use the --local flag if you prefer to use Local zone.

AWS credentials and configuration

cw uses the default credentials profile (stored in ./aws/credentials) for authentication and shared config (.aws/config) for identifying the target AWS region. Both profile and region are overridable via the profile and region global flags.

AWS SSO

AWS SSO is supported if you:

• use a CLI profile (either default or an alternate named profile) that includes the various SSO properties
  • sso_start_url, sso_account_id, sso_role_name, etc
• have a valid, active SSO session
  • via aws sso login

If you get an error message that includes ...failed to sign request: failed to retrieve credentials: the SSO session has expired or is invalid... then you should renew your SSO session via aws sso login (and specify the named profile, if appropriate).

Miscellaneous

Use cw behind a proxy

Please use HTTP_PROXY environment variable as required by AWS cli: https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-proxy.html

Breaking changes notes

Read here