frep

Generate file using template from environment, arguments, json/yaml/toml config files.

NAME:
   frep - Generate file using template

USAGE:
   frep [options] input-file[:output-file] ...

VERSION:
   1.3.x

AUTHORS:
   Guoqiang Chen <subchen@gmail.com>

OPTIONS:
   -e, --env name=value    set variable name=value, can be passed multiple times
       --json jsonstring   load variables from json object string
       --load file         load variables from json/yaml/toml file
       --no-sys-env        exclude system environments, default false
       --overwrite         overwrite if destination file exists
       --dryrun            just output result to console instead of file
       --strict            exit on any error during template processing
       --delims value      template tag delimiters (default: {{:}})
       --missing           handling of missing vars, one of: default/invalid, zero, error (default: default)
       --help              print this usage
       --version           print version information

EXAMPLES:
   frep nginx.conf.in -e webroot=/usr/share/nginx/html -e port=8080
   frep nginx.conf.in:/etc/nginx.conf -e webroot=/usr/share/nginx/html -e port=8080
   frep nginx.conf.in --json '{"webroot": "/usr/share/nginx/html", "port": 8080}'
   frep nginx.conf.in --load config.json --overwrite
   echo "{{ .Env.PATH }}"  | frep -

Downloads

v1.3.13 Release: https://github.com/subchen/frep/releases/tag/v1.3.13

• Linux

  curl -fSL https://github.com/subchen/frep/releases/download/v1.3.13/frep-1.3.13-linux-amd64 -o /usr/local/bin/frep
  chmod +x /usr/local/bin/frep
  
  # centos / redhat
  yum install https://github.com/subchen/frep/releases/download/v1.3.13/frep-1.3.13-204.x86_64.rpm
  
  # ubuntu
  curl -fSL https://github.com/subchen/frep/releases/download/v1.3.13/frep_1.3.13-204_amd64.deb -o frep_1.3.13-204_amd64.deb
  dpkg -i frep_1.3.13-204_amd64.deb
  

• macOS

  brew install subchen/tap/frep
  

• Windows

  wget https://github.com/subchen/frep/releases/download/v1.3.13/frep-1.3.13-windows-amd64.exe
  

Docker

You can run frep using docker container

docker run -it --rm subchen/frep --help

Examples

Load template variables

• Load from environment

  export webroot=/usr/share/nginx/html
  export port=8080
  frep nginx.conf.in
  

• Load from arguments

  frep nginx.conf.in -e webroot=/usr/share/nginx/html -e port=8080
  

• Load from JSON String

  frep nginx.conf.in --json '{"webroot": "/usr/share/nginx/html", "port": 8080}'
  

• Load from JSON file

  cat > config.json << EOF
  {
    "webroot": "/usr/share/nginx/html",
    "port": 8080,
    "servers": [
      "127.0.0.1:8081",
      "127.0.0.1:8082"
    ]
  }
  EOF
  
  frep nginx.conf.in --load config.json
  

• Load from YAML file

  cat > config.yaml << EOF
  webroot: /usr/share/nginx/html
  port: 8080
  servers:
    - 127.0.0.1:8081
    - 127.0.0.1:8082
  EOF
  
  frep nginx.conf.in --load config.yaml
  

• Load from TOML file

  cat > config.toml << EOF
  webroot = /usr/share/nginx/html
  port = 8080
  servers = [
     "127.0.0.1:8081",
     "127.0.0.1:8082"
  ]
  EOF
  
  frep nginx.conf.in --load config.toml
  

Input/Output

• Input from file

  // input file: nginx.conf
  frep nginx.conf.in
  

• Input from console(stdin)

  // input from stdin pipe
  echo "{{ .Env.PATH }}" | frep -
  

• Output to default file (Removed last file ext)

  // output file: nginx.conf
  frep nginx.conf.in --overwrite
  

• Output to the specified file

  // output file: /etc/nginx.conf
  frep nginx.conf.in:/etc/nginx.conf --overwrite -e port=8080
  

• Output to console(stdout)

  frep nginx.conf.in --dryrun
  frep nginx.conf.in:-
  

• Output multiple files

  frep nginx.conf.in redis.conf.in ...
  

Template

Templates use Golang text/template.

You can access environment variables within a template

Env.PATH = {{ .Env.PATH }}

If your template file uses {{ and }} as part of it's syntax, you can change the template escape characters using the --delims.

frep --delims "<%:%>" ...

There are some built-in functions as well: Masterminds/sprig v2.22.0

• github: https://github.com/Masterminds/sprig
• doc: http://masterminds.github.io/sprig/

More funcs added:

• toJson
• toYaml
• toToml
• toBool
• fileSize
• fileLastModified
• fileGetBytes
• fileGetString
• fileExists
• include
• countRune
• pipeline compatible regex functions from sprig
  • reReplaceAll
  • reReplaceAllLiteral
  • reSplit
• awsSecret
• awsParameterStore

Sample of nginx.conf.in

server {
    listen {{ .port }} default_server;

    root {{ .webroot | default "/usr/share/nginx/html" }};
    index index.html index.htm;

    location /api {
        {{ include "shared/log.nginx" | indent 8 | trim }}
        proxy_pass http://backend;
    }
}

upstream backend {
    ip_hash;
{{- range .servers }}
    server {{.}};
{{- end }}
}

Sample using secrets, first of all take into account that in order to use the secret functionality you need to have a proper AWS configuration in place and permissions enough to read secrets from AWS Secrets Manager. More details of how to configure AWSCLI can be found at https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-configure.html

Once you have all the requirements just create a template like this one:

# application.conf
mysql_host: {{ .mysql_host }}
mysql_user: {{ .mysql_user }}
mysql_pass: {{ awsSecret "application/mysql/password" }}

In above example mysql_host and mysql_user will be filled as usual by using frep config file or environment variables but mysql_pass will be fetch straight from AWS Secrets Manager by looking at secret name application/mysql/password

If you have multiple items in a single secret you can retrieve an specific key by specifying the key you want in template, for example:

# application.conf
mysql_host: {{ .mysql_host }}
mysql_user: {{ .mysql_user }}
mysql_pass: {{ awsSecret "application/mysql/password" }}

external_api_client: {{ awsSecret "application/external_api" "client_id" }}
external_api_secret: {{ awsSecret "application/external_api" "secret_key" }}

Sample using AWS Parameter Store, first of all take into account that in order to use the ssm functionality you need to have a proper AWS configuration in place and permissions enough to read parameters from AWS Parameter Store. More details of how to configure AWSCLI can be found at https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-configure.html

Once you have all the requirements just create a template like this one:

# application.conf
mysql_host: {{ .mysql_host }}
mysql_user: {{ .mysql_user }}
mysql_pass: {{ awsSecret "application/mysql/password" }}
mysql_dns: {{ awsParameterStore "application/mysql/dns" }}

In above example mysql_dns will be filled as usual by using frep config file or environment variables but mysql_pass will be fetch straight from AWS Parameter Store by looking at application/mysql/dns

SSM Limitation: You can get parameter from ParameterStore just in textplain.