Bash iterate over a list of strings

Question

I have this bash script:

for opt in string1 string2 string3 ... string99
do somestuff

It works, but I would like to replace the explicit listing of my strings with a file which actually contains all the strings; something like this:

strings=loadFromFile
for opt in $strings
do somestuff

How should I do this?

Answer 1

while read VAR is probably best here, as it handles per-line input. You can redirect it from a file, e.g.:

while IFS= read -r THELINE; do
  echo "..$THELINE"
done </path/to/file

That'll give you each line prepended with ".."

For your example case:

while IFS= read -r opt; do
  #somestuff $opt
done </path/to/file

See Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for explanations.

Answer 2

while IFS= read -r opt
do 
    some_stuff
done < file_with_string

See Why is `while IFS= read` used so often, instead of `IFS=; while read..`? for explanations.

Answer 3

The while IFS= read -r line; do ...; done < aFile is the best answer

If your strings do not contain whitespace or \[*?, you could do

for word in $(< aFile); do something; done

$(< file) is a bash feature that reads the file (like cat except without having to spawn a new process).

Answer 4

Why don't you use the readarray builtin (requires bash >= 4.0)?

readarray < FileNameFromWhereToLoad    # push every line of 
                                       # 'FileNameFromWhereToLoad' onto 
                                       # $MAPFILE by default

for i in $MAPFILE ; do
    echo $i
done

Answer 5

My advice:

cat INPUTFILE| {
  declare -a LINES
  mapfile -t LINES
  for line in "${LINES[@]}"
  do
    somestuff
  done
}