[SOLVED] sed terminated prematurely by presence of \c in input

porphyry5 · 06-17-2011, 09:46 AM

Sed seems to react to the presence of "\" in its input if the immediately following character makes the pair a recognizable code. In the code following see that the "\a" and "\b" are missing in the output, and that the "\c" caused sed to terminate at that point. Is there any way to prevent it reacting like this?

Code:

g  y="the shell built-in command. The following character sequences 
> have special meaning: 
> \a Alert (bell). 
> \b Backspace. 
> 
> \c Suppress trailing newline. 
> \f Form feed. 
> \n Newline. 
> \r Carriage return. 
> 
> \t Horizontal tab. 
> \v Vertical tab. 
> 
> \\ 
> Literal backslash. 
> \nnn 
> The octal character whose ASCII code is nnn. 
> Options"
g  z="the"
g  x="Options"
g  w=$(echo -e "$y"|sed -n -e "/$z/,/$x/ p")
g  echo "$w"
the shell built-in command. The following character sequences 
have special meaning: 
 Alert (bell). 
 Backspace. 
g

Same commands ready for pasting.

Code:

y="the shell built-in command. The following character sequences 
have special meaning: 
\a Alert (bell). 
\b Backspace. 

\c Suppress trailing newline. 
\f Form feed. 
\n Newline. 
\r Carriage return. 

\t Horizontal tab. 
\v Vertical tab. 

\\ 
Literal backslash. 
\nnn 
The octal character whose ASCII code is nnn. 
Options"
z="the"
x="Options"
w=$(echo -e "$y"|sed -n -e "/$z/,/$x/ p")
echo "$w"

druuna · 06-17-2011, 09:57 AM

Hi,

I don't think sed is the culprit, but the echo command is.

Try this: w=$(echo "$y"|sed -n -e "/$z/,/$x/ p")

The -e is removed, this from the echo man page:

Quote:

-e enable interpretation of backslash escapes

The -e in the sed command is also not needed in this case, but it doesn't do any harm.

Hope this helps.

porphyry5 · 06-17-2011, 10:03 AM

Quote:

Originally Posted by druuna

Hi,

I don't think sed is the culprit, but the echo command is.

Try this: w=$(echo "$y"|sed -n -e "/$z/,/$x/ p")

The -e is removed, this from the echo man page:

The -e in the sed command is also not needed in this case, but it doesn't do any harm.

Hope this helps.

Ah, thank you. I always include -e with echo so it will interpret the "\n"s, never thought about its extended meaning.

druuna · 06-17-2011, 10:05 AM

You're welcome