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KSXGitHub/first-line.ts

Created March 2, 2020 11:36
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  1. KSXGitHub created this gist Mar 2, 2020.
    19 changes: 19 additions & 0 deletions first-line.ts
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,19 @@
    import { createReadStream } from 'fs'
    import { createInterface } from 'readline'

    const READ_STREAM_OPTIONS = { encoding: 'utf8' } as const

    export function firstLine (filename: string) {
    const stream = createReadStream(filename, READ_STREAM_OPTIONS)
    const reader = createInterface(stream)
    let result: string
    reader.once('line', line => {
    result = line
    reader.close()
    })
    return new Promise<string>(resolve => {
    reader.once('close', () => resolve(result))
    })
    }

    export default firstLine