Bash while loop to read line upto ;-CodePudding

I have a text file like

line2
line3;
line4
line5
line6
line7;

I need a loop to read the line till ; on each loop. on the first loop read up to line3; and on the second loop up to line7; and so on. no need to merge the lines into a single one

CodePudding user response：

Consider telling read to stop on ; instead of on newlines, and instead to use newlines to delimit individual input items (when using -a to read into an array, this makes each line an array element).

When given your input,

while IFS=$'\n' read -r -d ';' -a lines; do
  echo "Read group of lines:"
  printf ' - %s\n' "${lines[@]};"
done

...emits as output:

Read group of lines:
 - line2
 - line3;
Read group of lines:
 - line4
 - line5
 - line6
 - line7;

You can, if you choose, replace the printf with something like for line in "${lines[@]}"; do to create an inner loop to operate on lines within a group one-by-one.

CodePudding user response：

You can use two loops: one to continue until the end of the file, and an inner loop to read individual lines until you find one that ends with a ;.

For example,

while :; do
    lines=()
    while IFS= read -r line; do
        lines =( "$line" )
        if [[ $line = *; ]]; then
            break
        fi
    done
    if (( ${#lines[@]} == 0 )); then
        # The previous loop didn't add anything to the array,
        # so the last read must have failed, and we've reached
        # then end of the file
        break
    done
    # do something with $lines
done < file.txt

Or, use one loop that pauses to use lines when one ending with a ; is found:

lines=()
while IFS= read -r line; do
    lines =("$line")
    if [[ $line = *; ]]; then
        # do stuff with lines, then clear the array
        lines=()
    fi
done < file.txt

# If applicable, do something with the last batch of lines
# if the file doesn't end with a ;-terminated line.