CODEWITHSUNDEEP
linuxbashsed
Guille
Guille

Reputation: 75

Execute sed command in a bash script

I want to execute this comand in bash scripting.

Code:

#!/bin/bash
line=39;
d=d; ## For delete line
`echo "sed '$line$d' /etc/passwd"`;

But when I execute, I got this error:

sed: -e expresion #1, character 1: unknow command <<'>>

I tried with echo "sed \'$line$d\' /etc/passwd";

But same problem...

Upvotes: 0

Views: 16127

Answers (3)

NeronLeVelu
NeronLeVelu

Reputation: 10039

#!/bin/bash

# delete line 39 by editing inline via sed;
sed -i '39d' /etc/passwd

Keep it simple and add the comment if you want remember the sed action

Upvotes: 0

ShellFish
ShellFish

Reputation: 4551

To delete line 39 simply do:

#!/bin/bash
line=39;
sed -i "${line}d" /etc/passwd

Sed will take the second argument as input file and the first as a command. The extra flag -i will allow you to redirect the output immediately to the input file. Note that this is not the same as sed 'command' file > file as this will result in an empty file.

I also advise executing man sed in your shell.

Upvotes: 1

David C. Rankin
David C. Rankin

Reputation: 84561

You need to insure when calling your variables that you do not prevent expansion by single-quoting them. Now it is OK to use single-quotes within double-quotes, but be mindful. Also, though not required, when putting two variables back-to-back, it is better to use braces to insure against ambiguity. That said, your sed command from a script works fine as:

sed -e "${line}${d}" /etc/passwd

Which will output /etc/passwd to stdout minus line $line. To edit /etc/passwd in place, use sed -i

Upvotes: 2

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