Useful bash snipetts

bash_regex_text.sh

re='^[0-9]+$'

if ![[ $yournumber =~ $re ]]; then
  echo "error: Not a number" >&2
fi

bash_selection_menu.sh

# to use the default "#?" as the indicator for
# input, remove the PS3 line

PS3="File: "

select FILENAME in *; do
  case $FILENAME in
    *) echo "You picked $FILENAME"
  esac
done

collegs_args.sh

ARGS=$@
LIST=${ARGS[@]/"$1"}

for i in ${LIST[@]}; do
  echo ${LIST[@]}
done

for i in ${LIST[@]}; do
  echo $i >> LIST.txt
done

delete_replace_last_line.sh

seq 1 1000000 | while read i; do echo -en "\r$i"; done

# from man echo:

# -n     do not output the trailing newline
# -e     enable interpretation of backslash escapes
# \r     carriage return

replace_in_line.sh

# replacing a line in a file.

# https://stackoverflow.com/questions/11145270/how-to-replace-an-entire-line-in-a-text-file-by-line-number

FILE='replace_in_file.txt'

echo "Lorem ipsum dolor sit amet," > $FILE
echo "consectetur adipiscing elit." >> $FILE
echo "Duis eu diam non tortor laoreet" >> $FILE
echo "bibendum vitae et tellus." >> $FILE

sed -e '2s/.*/new text/' -i $FILE
#       ^
# where N should be replaced by your target line number. 
# This replaces the line in the original file.
# To save the changed text in a different file, drop the -i option:

# sed -e '2s/.*/new text/' $FILE