I need to combine the first value ($1) of consecutive rows if their fourth value ($4) is the same (I-PER).

I managed to filter the values I need simply using awk:

awk ' ($4 == "I-PER") {printf $1; printf "

" }

I also found how to merge rows with duplicate column values but not consecutive ones.

Example (Input):

Comandante  comandante  NP00000 I-PER

de  de  SPS00   I-PER

la  el  DA0FS0  I-PER

Guardia guardia NP00000 I-PER

Civil   civil   NP00000 I-PER

Pamplona    pamplona    NP00000 I-LOC

Poblador    poblador    NP00000 I-PER

Example (Output):

Comandante de la Guardia Civil

Poblador