View source for variable usage in sed commands


Example

print only lines 2 through 4 of file

$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n '2,4p''''
<br>two
<br>three
<br>four

same using variables

START=2
<br>END=4

$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "${START},${END}p"'''
<br>two
<br>three
<br>four

Examples that FAIL...

$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "$START,$ENDp"'''
sed: -e expression #1, char 2: unexpected `,'

solution is to include the curly braces around the variable names


$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n '${START},${END}p''''
<br>sed: -e expression #1, char 3: unknown command: `S'

solution is to use double quotes in the sed commands so the variables are expanded

[[category:sed]]