glin

glin

Go line scanner

Glin is similar in concept to "awk" but offers a more limited and simplified interface.

Glin reads lines from standard input, splits each line into fields, and writes a re-ordered list of fields.

A common usage for glin is to "filter" a log file and return only a limited set of fields.

usage

glin  [options] [output field list]

Options:
  -after string
        process fields in line after specified tag (remove text before tag)
  -after-line string
        process lines after lines that matches
  -after-linen int
        process lines after n lines
  -before string
        process fields in line before specified tag (remove text after tag)
  -before-line string
        process lines before lines that matches
  -begin string
        expression to be executed before processing lines
  -contains string
        output only lines that contains the pattern
  -debug
        print debug info
  -end string
        expression to be executed after processing lines
  -expr string
        expression to be executed for each line
  -grep string
        output only lines that match the regular expression
  -ifn int
        maximum number of fields when splitting input (<1=all) (default -1)
  -ifs string
        input field separator (default " ")
  -ifs-re string
        input field separator (as regular expression)
  -line
        print line numbers
  -matches string
        return status code 100 if any line matches the specified pattern, 101 otherwise
  -ofs string
        output field separator (default " ")
  -print-expr
        print result of -expr
  -printf string
        output is formatted according to specified format
  -quote
        quote returned fields
  -re string
        regular expression for parsing input
  -remove
        remove specified fields instead of selecting them
  -shlex
        split using shlex/shell-style rules
  -test string
        test expression (skip line if false)
  -ucount
        print unique lines (and count)
  -uniq
        print only unique lines
  -unquote
        quote returned fields
  -version
        print version and exit

Output field list: one or more indices (or slices) of fields to return. Also, use `{{expr}}` to return the current value of `-expr` or `{{expr:varname}}` to return the value of variable `varname`.

Expressions use the syntax described here with the following additions:

• It's possible to set variables:

  name=expr
  

  And use variables:

  $name
  

• The following variables are predefined (same as awk):

  • $NR : current number of records / lines
  • $NF : number of fields in the current line
  • $0 : the current line
  • $1 to $NF: the value of the numbered field

• The following functions are available:

  • print(args...) : print one or more arguments
  • format(fmt, args...) : format one or more arguments according to fmt (like sprintf)
  • num("string") : convert string to float, to apply numeric operations
  • int("string") : convert string to int, to apply numberic operations
  • len("string") : return length of string
  • substr("string", start, [len]) : return substring of string starting from start (truncate to len characters if `len is specified)

Also:

• Slices follow the Go slice convention (start:end) or better, the Python slice convention (negative values are offsets from the end, so -1 is the last field).
• Field 0 is the input line (as in "awk") so the various fields are indexed from 1 to the number of fields.