Difference between revisions of "variable usage in sed commands"
From thelinuxwiki
Line 13: | Line 13: | ||
$ '''START=2''' | $ '''START=2''' | ||
<br>$ '''END=4''' | <br>$ '''END=4''' | ||
− | + | <br>$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "${START},${END}p"''' | |
− | $ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "${START},${END}p"''' | + | |
<br>two | <br>two | ||
<br>three | <br>three |
Revision as of 20:11, 24 January 2018
Example
print only lines 2 through 4 of file
$ printf "one\ntwo\nthree\nfour\nfive\n" | sed -n '2,4p'
two
three
four
same using variables
$ START=2
$ END=4
$ printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "${START},${END}p"
two
three
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'
sed: -e expression #1, char 3: unknown command: `S'
solution is to use double quotes in the sed commands so the variables are expanded