问题
I try to use sed to change a line in a file named convergence.gnu
I have a variable named lafila, which is a file name
Currently, I can do:
lafila="nGas060.dat"
sed -i "6s/.*/plot \"$lafila\" using 1:2 with l/" convergence.gnu
This changes correctly the sixth line of my convergence.gnu file to:
plot "nGas062.dat" using 1:2 with l
However, now I want to include a dollar sign in the replaced line to obtain instead:
plot "nGas062.dat" using ($1/1000):2 with l
Can you tell me what to change in my sed command? If I escape a dollar sign it does not work properly. Double dollars also don't work.
回答1:
Use single quotes:
sed -i '6s/.*/plot "'$lafila'" using ($1\/1000):2 with l/' convergence.gnu
Single quotes protect double quotes and $ is not interpreted inside them. However, you do need to escape /.
See also:
- Difference between single and double quotes in Bash
回答2:
I believe your issue is actually being caused by the forward slash in ($1/1000), which clashes with the slashes being used to delimit the various components of the sed command. You either need to escape that forward slash as well, or alternatively use a different character for delimiting the sed strings. Either of the below should work:
lafila="nGas060.dat"
sed -i "6s/.*/plot \"$lafila\" using (\$1\/1000):2 with l/" convergence.gnu
or
lafila="nGas060.dat"
sed -i "6s,.*,plot \"$lafila\" using (\$1/1000):2 with l," convergence.gnu
Using a different delimiting character can be a good way to make your sed string look neater and avoid the leaning toothpick syndrome.
echo foo | sed "s,foo,/there/are/a/lot/of/slashes/here,"
is much nicer than
echo foo | sed "s/foo/\/there\/are\/a\/lot\/of\/slashes\/here/"
回答3:
Try it:
lafila="nGas060.dat"
sed -i "6s@.*@plot \"$lafila\" using (\\\$1/1000):2 with l@" convergence.gnu
You need only to escape backslash and after the dollar sign.
\\ + \$ == \\\$
来源：https://stackoverflow.com/questions/46842495/using-dollar-sign-in-sed-for-both-variable-replacement-and-character