title: Using tee and grep to save certain lines of output to a file
body: <p>I want to see the entire output of my script but only save lines matching "vlim" to a new file. I've nearly figured it out but can't quite get it to work the way I want it  to. I'm currently stuck between using:</p>
  
  <pre><code>python gmakemovie.test movie.cfg.test --overwrite | tee &gt;(grep vlim) /output.txt
  grep vlim output.txt &gt; vlim.txt
  </code></pre>
  
  <p>or</p>
  
  <pre><code>python gmakemovie.test movie.cfg.test --overwrite | grep vlim | tee  /output.txt
  </code></pre>
  
  <p>The top option shows my entire output but also copies all of the output to output.txt. The bottom option copies only "vlim" but doesn't show the rest of my output, so I can't tell where I am in my script.</p>
  
  <p>For clarity, this is what my output looks like:</p>
  
  <pre><code>imported pygad v0.4.32+ga1eacb4.dirty
  from parameter file (fragmentary):
    snaps:      200 - 200
    width:      1000.0 [kpc]
    pixel:      500 x 500
    x - y:      x - y
    softening:  [  0.2    0.45   2.52  20.     0.2    0.2 ] [ckpc h_0**-1]
  ====================================================
  get orientation from trace file "filepath":
    L:       [ 241.01309204  544.96875    -366.44366455] [1e+10 ckpc h_0**-1      Msol h_0**-1 km s**-1]
  get first non-zero center from trace files
    from snapshot 200:
    center:  [ 36821.75390625  35120.65625     33730.06640625] [ckpc h_0**-1]
  ====================================================
  run in serial
  ====================================================
  read snapshot "filepath"
    z = 2.84615386294
    t = 2.33634681236 [Gyr]
  get center and orientation from trace file "filepath":
    center:  [ 36821.75390625  35120.65625     33730.06640625] [ckpc h_0**-1]
    R200:    47.4815177362 [kpc]
  center snapshot
  orientate snapshot
  render...
    axis 1: stars...
    im_lum = np.log10(im_lum)
  vlim: [-6.59883562 -4.09629962]
    np.ndarray.__idiv__(self, x)
    axis 2: gas...
  vlim: [-0.46031536  0.83438775]
  </code></pre>
  
  <p>and I want the output file to look like:</p>
  
  <pre><code>vlim: [-6.59883562 -4.09629962]
  vlim: [-0.46031536  0.83438775]
  </code></pre>
  
  <p>I'm working in the terminal on my mac</p>