Difference between revisions of "variable usage in sed commands"
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same using variables | same using variables | ||
| − | 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 | ||
| Line 22: | Line 21: | ||
$ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "$START,$ENDp"''' | $ '''printf "one\ntwo\nthree\nfour\nfive\n" | sed -n "$START,$ENDp"''' | ||
| − | sed: -e expression #1, char 2: unexpected `,' | + | <br>sed: -e expression #1, char 2: unexpected `,' |
solution is to include the curly braces around the variable names | solution is to include the curly braces around the variable names | ||
Latest revision as of 20:12, 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
