jq-printf

jq module implementing printf function

Usage

The printf/1 function is used by passing the format string as a function argument, with inputs interpreted as format values.

$ jq -n '
include "printf";
["bird", 5.55] | printf("%-6s is the word the number is %+05.1f")
'
"bird   is the word the number is +05.6"

This printf implementation is written to be forgiving of input types, and accept null, string, list, number and object inputs. If a format value does not match a corresponding format type, it generally prints as a string. As jq does not have number types (there is no distinction between a float and an integer; much less integer lengths or sign/unsigned types), some handling has been built into the implementation.

A subset of standard printf format types and modifiers are currently supported, and the framework is in place to easily add more.

Flags

As in %<flag><type> (ex: %+f):

• - left adjustment within the field width
• + force adding sign when used with %d, %i or %f
• 0 zero padding used to fill out remaining field width

Field Width

As in %<field_width><type> (ex: %10s) specifies minimum field width, which will be left padded (right aligned) unless the left adjustment flag is specified (ex: %-10s).

Precision

As in %.<precision><type> (ex: %.3f) specifies the precision for floating point numbers. Integers or floating points specified with lower precision are zero padded; floating points specified with greater precision are rounded.

Types

The following types are supported:

• d or i - signed decimal or integer
• f - floating point number
• s - string
• % - escape sequence, prints a literal %

Debugging

To debug, change your printf function call to __printf. The .history list of objects will show the state of parsing and formatting at each pass.

License

printf is released under the MIT license.