Command line

bafi -i INPUT -t TEMPLATE [-o OUTPUT]
COMMAND | bafi -f FORMAT -t TEMPLATE

bafi -h prints the same overview with all flags.

Flags

Flag Meaning
-i file Input file. Without -i, bafi reads standard input (a pipe or < file). -i '?list.yaml' reads several files.
-t template Template file, or an inline template starting with ?: -t '?{{toJSON .}}'.
-o file Output file. Without -o, the result goes to standard output.
-f format Input format: json, bson, yaml, csv, xml, mt940. Default: from the -i file extension. Required for standard input.
-d delimiter CSV delimiter: one character (-d ';') or a hex byte (-d 0x09 for TAB). Default ,. For MT940, the separator between messages.
-strict Fail on a key that is missing from the input instead of printing <no value>.
-v Print the version.
-h Print help.
-gq question Ask OpenAI about the input instead of using a template. See Ask OpenAI.
-gk key OpenAI API key. Default: the OPENAI_API_KEY environment variable (preferred).
-gm model OpenAI model: gpt35 (default), gpt4, gpt4o, gpt4o-mini, gpt5, gpt5mini, gpt5nano.

Flags must come before any other argument.

Input

bafi -i testdata.xml -t '?{{index .TOP_LEVEL "-description"}}'

employeeData

The format is taken from the extension: .json, .bson, .yaml/.yml, .csv, .xml (also .cdf, .cdf3), .sta (MT940). -f overrides it. Standard input has no name, so -f is required:

curl -fs https://example.com/api/users | bafi -f json -t users.tmpl

Redirecting a file works the same way:

{"users": [{"name": "Alice"}, {"name": "Bob"}]}

bafi -f json -t '?{{len .users}} users' < users.json

2 users

A single - after the flags, the usual "read standard input" marker, is accepted and changes nothing.

A UTF-8 byte order mark at the start of the input is ignored.

Several input files

-i '?list.yaml' reads every file named in a YAML list and makes each available under its label (quote it: zsh, the macOS default shell, treats an unquoted ? as a wildcard):

- file: rates.xml
  label: RATES          # {{ .RATES }}
- file: orders.json
  label: ORDERS
  format: json          # optional; the extension decides when omitted

-f is ignored in this mode; -d applies to every CSV file. Full example: Merge several files into one output.

Templates on the command line

An inline template starts with ?. Quote it so the shell passes it as one argument:

Shell Example
bash, zsh bafi -i data.json -t '?{{toXML .}}'
PowerShell .\bafi.exe -i data.json -t "?{{toXML .}}"
cmd.exe bafi.exe -i data.json -t "?{{toXML .}}"

Inside single quotes, template strings use double quotes: -t '?{{index . "my-key"}}'. A template file avoids quoting issues altogether: -t report.tmpl. The template guide explains the syntax.

Output

The result goes to standard output unless -o names a file. bafi renders the whole result first: when a template fails, standard output stays empty and an existing -o file is left as it was, so a pipe never receives half a document and a scheduled job keeps its last good report.

Append to a file with the shell:

bafi -i testdata.xml -t template.tmpl >> output.txt

Errors, warnings and exit codes

Errors and warnings go to standard error, never into the output. An error names the file and line, shows the problem and suggests a fix; see Troubleshooting.

Exit code Meaning
0 Success (warnings may have been printed).
1 The input, the template, the output file or the OpenAI request failed.
2 The command line is wrong: missing template or input, unknown flag or format.

Warnings do not change the output or the exit code:

  • the output contains <no value> because the template used a key the input does not have;
  • a CSV header ended up as a single column, which usually means the wrong -d.

Strict mode

-strict turns a missing key into an error with the key name and the template line, instead of printing <no value>:

bafi -i testdata.xml -strict -t '?{{.TOP_LEVEL.DATA_LINES}}'

bafi: template error in the inline template (line 1, column 3)

  1 | {{.TOP_LEVEL.DATA_LINES}}
    |   ^
  map has no entry for key "DATA_LINES" (at <.TOP_LEVEL.DATA_LINES>)

hint: the input has no key "DATA_LINES" here (-strict is on); check spelling and case - XML attributes start with "-" (index . "-id"); for keys that may be absent use {{with index . "DATA_LINES"}}...{{end}}
docs: https://mmalcek.github.io/bafi/troubleshooting/#missing-keys-and-no-value

Use it while writing a template, and in automation where a missing field must not go unnoticed. For keys that may legitimately be absent, use index: {{with index . "nickname"}}{{.}}{{end}}.