# NGLess Constants

In NGLess, any variable written in uppercase is a constant, i.e., can only be assigned to once. In addition, there are builtin constants defined by NGLess.

## Built in constants

  • ARGV

This is string array which contains the arguments passed to the script

  • STDIN

Use in place of a filename to read from standard input

  • STDOUT

Use in place of a filename to write to standard output

For example:

ngless ‘0.9’

input = samfile(STDIN) input = select(input) using |mr|:

if mr.flag({mapped}):
discard

write(input, ofile=STDOUT, format={bam})

This file reads a sam stream from stdin, filters it (using the select call) and writes to standard output in bam format.

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