field_opts - Linux


The field_opts tool parses a sequence of whitespace-separated fields from its input and applies transformations to these fields based on a user-defined format specification. It is commonly used for extracting specific data fields from text files or data streams.


field_opts [options] <field_parser> <input_file | input_string>


  • <field_parser>: A string specifying the field parsing format.
  • <input_file | input_string>: The input file or string to parse. If omitted, reads from STDIN.


  • **-d `: Specify a custom field delimiter (default: whitespace).
  • **-s `: Specify a separator to insert between parsed fields (default: none).
  • **-n <num_fields>`: Limit the number of fields to parse from each line.
  • **-v`: Print verbose output, including parsing errors.
  • **-h, –help`: Display usage information and exit.


1. Extracting fields from a CSV file

field_opts -d ',' -s ':' -n 2 name,age addresses.csv

2. Tokenizing words from a string

field_opts word_tokenize "This is a sample string to tokenize."

3. Limiting the number of parsed fields

field_opts -n 3 "%6s %*s %*s" "This is a line with multiple whitespace-separated fields."

Common Issues

1. Incorrect field parsing

Ensure the format string correctly matches the input data structure to avoid unexpected parsing results.

2. Missing input

Specify an input file or string, or the command will read from STDIN, which may be empty.


Field_opts can be used as part of pipelines or scripts:

cat file.txt | field_opts -d ',' > parsed.csv

Related Commands

  • cut: Select specific columns from text data.
  • grep: Search for specific patterns within text data.
  • sed: Perform text transformations and substitutions.