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I am trying to change the whole line in a file matched by part of the line only. e.g. the command below works fine as "$Netconf_DHCPStart" doesn't have a / in it:

sed -e '/DHCP_START=/c\DHCP_START='"$Netconf_DHCPStart"

However, the command below doesn't work 

sed '/static ip_address='"${Current_StaticIP}"'/c\static ip_address='"$Netconf_range"'.110' /etc/dhcpcd.conf

giving error:

sed: -e expression #1, char 32: unknown command: '2'

I know that this is because "$Current_StaticIP" contains a / within it, however, I am not sure how to format it so it will work. Do I need to escape the \ within the variable first?

don_crissti
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Josh
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    Hi @Josh. Kindly would you please include example of the input and output. This will make the question very helpful to everyone. –  Sep 19 '18 at 14:20
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    Contents of variables would be nice, too. – RudiC Sep 19 '18 at 14:21
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    Linkin in: https://unix.stackexchange.com/questions/32907/what-characters-do-i-need-to-escape-when-using-sed-in-a-sh-script – Jeff Schaller Sep 19 '18 at 14:25
  • I believe Josh has clearly identified the problem: the $Current_StaticIP variable contains a forward-slash, prematurely ending the /static ip_address.../ search – Jeff Schaller Sep 19 '18 at 14:27
  • Sorry should have included them. $Netconf_DHCPStart is 192.168.0.111. $Current_StaticIP is 192.168.0.5 and $Netconf_range is 192.168.0. – Josh Sep 19 '18 at 15:10
  • Whoops - $Current_StaticIP is 192.168.0.5/24 – Josh Sep 19 '18 at 15:17

1 Answers1

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You could use the alternative \c...c form, where c is any character that isn't expected to come up inside your variable:

sed '\%static ip_address='"${Current_StaticIP}"'%c\static ip_address='"$Netconf_range"'.110'

(The c\ part of your sed command isn't the problem unless your second variable contains a newline.)

JigglyNaga
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  • That worked perfectly. Although the second variable doesn't contain a newline that I'm aware of - its simply 192.168.0.5/24 – Josh Sep 19 '18 at 15:34
  • By "second variable" I mean $Netconf_range, the one after c\... But as previously stated, that's not the problem here. – JigglyNaga Sep 19 '18 at 15:35
  • Sorry looking at way too many variables at the moment. Netconf_range is 192.168.0 Anyway the % worked perfectly. Thanks for your help. – Josh Sep 19 '18 at 15:40