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tj - stdin line timestamps, JSON-friendly

tj timestamps lines read from standard input.

Get it

Using go get:

go get -u

Or download the binary from the releases page:

# Linux
curl -L | tar xz

# OS X
curl -L | tar xz

# Windows
curl -LO

Also available as a docker image:

docker pull

Use it

tj reads from stdin and writes to stdout.

Usage of tj:
  -template string
    	either a go template ( or one of the predefined template names
  -time-format string
    	either a go time format string or one of the predefined format names (
  -time-zone string
    	time zone to use (or "Local") (default "UTC")
  -match-regex string
    	a regex pattern. if given, only tokens matching it (re)start the stopwatch
  -match-template string
    	go template, used to extract text used for -match-regex
  -match-condition string
    	go template. if given, only tokens that result in 'true' (re)start the stopwatch
    	buffer lines between matches of -match-regex / -match-condition, copy delta values from final line to buffered lines
  -match string
    	alias for -match-template
  -condition string
    	alias for -match-condition
  -regex string
    	alias for -match-regex
    	parse a sequence of JSON objects from stdin
  -scale string
    	either a sequence of hex colors or one of the predefined color scale names (colors go from fast to slow)
      (default "BlueToRed")
  -scale-fast duration
    	the lower bound for the color scale (default 100ms)
  -scale-slow duration
    	the upper bound for the color scale (default 2s)
    	use linear scale (default true)
    	use cubic scale
    	use cubic root scale
    	use quadratic scale
    	use quadratic root scale
    	print version and exit

JSON output

The default output format is JSON, one object per line:

$ (echo Hello; echo World) | tj

Time format

You can set the format of the time field using the -time-format parameter:

$ (echo Hello; echo World) | tj -time-format Kitchen

The constant names from pkg/time as well as regular go time layouts are valid values for -time-format:

Name Format
ANSIC Mon Jan _2 15:04:05 2006
Kitchen 3:04PM
ISO8601 2006-01-02T15:04:05Z07:00
RFC1123 Mon, 02 Jan 2006 15:04:05 MST
RFC1123Z Mon, 02 Jan 2006 15:04:05 -0700
RFC3339 2006-01-02T15:04:05Z07:00
RFC3339Nano 2006-01-02T15:04:05.999999999Z07:00
RFC822 02 Jan 06 15:04 MST
RFC822Z 02 Jan 06 15:04 -0700
RFC850 Monday, 02-Jan-06 15:04:05 MST
RubyDate Mon Jan 02 15:04:05 -0700 2006
Stamp Jan _2 15:04:05
StampMicro Jan _2 15:04:05.000000
StampMilli Jan _2 15:04:05.000
StampNano Jan _2 15:04:05.000000000
UnixDate Mon Jan _2 15:04:05 MST 2006

Template output

You can also specify an output template using the -template parameter and go template syntax:

$ (echo Hello; echo World) | tj -template '{{ .I }} {{.TimeSecs}} {{.Text}}'
0 1516649679 Hello
1 1516649679 World

The fields available to the template are specified in the token struct.

Some templates are pre-defined and can be used via -template NAME:

Name Template
Color {{color .}}█{{reset}} {{.Text}}
ColorText {{color .}}{{.Text}}{{reset}}
Delta {{.Delta}} {{.Text}}
DeltaColor {{.Delta}} {{color .}}█{{reset}} {{.Text}}
DeltaNanos {{.DeltaNanos}} {{.Text}}
Text {{.Text}}
Time {{.TimeString}} {{.Text}}
TimeColor {{.TimeString}} {{color .}}█{{reset}} {{.Text}}
TimeDelta {{.TimeString}} +{{.Delta}} {{.Text}}
TimeDeltaNanos {{.TimeString}} +{{.DeltaNanos}} {{.Text}}

Color output

To help identify durations at a glance, tj maps durations to a color scale. The pre-defined templates Color and ColorText demonstrate this:

$ (echo fast; 
   sleep 1; 
   echo slower; 
   sleep 1.5; 
   echo slow; 
   sleep 2; 
   echo slowest) | tj -template Color

Color output

The terminal foreground color can be set by using {{color .}} in the output template. The default terminal color can be restored using {{reset}}.

The color scale can be set using the parameters -scale, -scale-fast, and -scale-slow:

  • The -scale parameter defines the colors used in the scale.
  • The -scale-fast and -scale-slow parameters define the boundaries of the scale: durations shorter than the value of -scale-fast are mapped to the leftmost color, durations longer than the value of -scale-slow are mapped to the rightmost color.

The scale is linear by default, but can be transformed:

  • -scale-sqr, -scale-sqrt yields a quadratic (root) scale
  • -scale-cube, -scale-cubert yields a cubic (root) scale

There are several pre-defined color scales:

Name Scale
BlackToPurple #000 -> #F700FF
BlackToRed #000 -> #F00
BlueToRed #00F -> #F00
CyanToRed #0FF -> #F00
GreenToRed #0F0 -> #F00
GreenToGreenToRed #0F0 -> #0F0 -> #F00
WhiteToPurple #FFF -> #F700FF
WhiteToRed #FFF -> #F00
WhiteToBlueToRed #FFF -> #00F -> #F00

You can also provide your own color scale using the same syntax as the pre-defined ones.

JSON input

Using -read-json, you can tell tj to parse stdin as a sequence of JSON objects. The parsed object can be referred to via .Object, like this:

$ echo '{"hello": "World"}' | tj -read-json -template "{{.TimeString}} {{.Object.hello}}"
2018-01-25T21:55:06+01:00 World

The exact JSON string that was parsed can be recovered using .Text:

$ echo '{"hello"   :    "World"} {   }' | tj -read-json -template "{{.TimeString}} {{.Text}}"
2018-01-25T21:55:06+01:00 {"hello"   :    "World"}
2018-01-25T21:55:06+01:00 {   }

Stopwatch regex

Sometimes you need to measure the duration between certain tokens in the input.

To help with this, tj can match each line against a regular expression and only reset the stopwatch (delta, deltaSecs, deltaNanos) when a line matches. The regular expression can be specified via the -match-regex (alias -regex) parameter.

Stopwatch regex template

When using -match-regex, you can also specify a template -match-template (alias -match) to extract text from the current token. The output of this template is matched against the stopwatch regex.

This allows you to use only specific fields of JSON objects as stopwatch reset triggers. For example:

$ (echo {}; sleep 1; echo {}; sleep 1; echo '{"reset": "yes"}'; echo {}) | 
    tj -read-json -match .reset -regex yes -template "{{.I}} {{.DeltaNanos}}"
0 14374
1 1005916918
2 2017292187
3 79099

The output of the match template is stored in the field .MatchText of the token struct:

$ echo '{"message":"hello"}' | tj -read-json -match-template .message -template "{{.TimeString}} {{.MatchText}}"
2018-01-25T22:20:59+01:00 hello

Stopwatch condition

Additionally to -match-regex, you can specify a -match-condition go template. If this template produces the literal string true, the stopwatch is reset - "matches" of the -match-condition are treated like matches of the -match-regex.


Finding the slowest step in a docker build (using jq):

$ cat Dockerfile
FROM alpine
RUN echo About to be slow...
RUN sleep 10
RUN echo Done being slow
$ docker build . |
    tj -regex ^Step |
    jq -s 'max_by(.deltaNanos) | {step:.start.text,}'
{"step":"Step 3/4 : RUN sleep 10","duration":"10.602026127s"}

Alternatively, using color output and buffering:

$ docker build . |
    tj -regex ^Step -match-buffer -template Color -scale-cube

Docker build with color output


Feel free to leave a comment or create an issue.


stdin line timestamps. single binary, no dependencies. osx & linux & windows. plays well with jq.




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