How to read lines from a file into an array?

Question

I'm trying to read in a file as an array of lines and then iterate over it with zsh. The code I've got works most of the time, except if the input file contains certain characters (such as brackets). Here's a snippet of it:

#!/bin/zsh
LIST=$(cat /path/to/some/file.txt)
SIZE=${${(f)LIST}[(I)${${(f)LIST}[-1]}]}
POS=${${(f)LIST}[(I)${${(f)LIST}[-1]}]}
while [[ $POS -le $SIZE ]] ; do
    ITEM=${${(f)LIST}[$POS]}
    # Do stuff
    ((POS=POS+1))
done

What would I need to change to make it work properly?

Answer 1

#!/bin/zsh
zmodload zsh/mapfile
FNAME=/path/to/some/file.txt
FLINES=( "${(f)mapfile[$FNAME]}" )
LIST="${mapfile[$FNAME]}" # Not required unless stuff uses it
integer POS=1             # Not required unless stuff uses it
integer SIZE=$#FLINES     # Number of lines, not required unless stuff uses it
for ITEM in $FLINES
    # Do stuff
    (( POS++ ))
done

You have some strange things in your code:

1. Why are you splitting LIST each time instead of making it an array variable? It is just a waste of CPU time.
2. Why don’t you use for ITEM in ${(f)LIST}?
3. There is a possibility to directly ask zsh about array length: $#ARRAY. No need in determining the index of the last occurrence of the last element.
4. POS gets the same value as SIZE in your code. Hence it will iterate only once.
5. Brackets are problems likely because of 3.: (I) is matching against a pattern. Do read documentation.