sed : difference csh/sh to append a line

[larrun]

Hi,

I have the file 'file.txt' :

nadal
federer
delpotro

I want to use the append line command 'a\' of 'sed' to append the 2 following lines:

wimbledon
USopen

after the 'federer' line

under sh, I execute :
$ sed '/federer/a\
> wimbledon\
> USopen' file.txt

Result OK :
nadal
federer
wimbledon
USopen
delpotro

To get the same result under csh, I have to execute :
sed '/federer/a\\
? wimbledon\\
? USopen' file.txt

why do I have to double the '\' character ?
Is it related to the shell ? the sed program (I am using the same GNU version 4.0.7 under Linux) ?

Any idea ?

thanks

[robertdaleweir]

Hi,

I have the file 'file.txt' :

nadal
federer
delpotro

I want to use the append line command 'a\' of 'sed' to append the 2 following lines:

wimbledon
USopen

after the 'federer' line

under sh, I execute :
$ sed '/federer/a\
> wimbledon\
> USopen' file.txt

Result OK :
nadal
federer
wimbledon
USopen
delpotro

To get the same result under csh, I have to execute :
sed '/federer/a\\
? wimbledon\\
? USopen' file.txt

why do I have to double the '\' character ?
Is it related to the shell ? the sed program (I am using the same GNU version 4.0.7 under Linux) ?

Any idea ?

thanks

Hi larrun
I have taken a snippet from the man pages of 'sh' and from 'csh' to possibly help understand the reason. Different 'Parser Engines' are used for sh and csh (possibly tcsh).

sh
When the old-style backquote form of substitution is used, backslash retains its literal meaning except when followed by $, `, or \. The first backquote not preceded by a backslash terminates the command substitution. When using the $(command) form, all characters between the parentheses make up the command; none are treated specially.

csh
A special character (including a blank or tab) may be prevented from having its special meaning, and possibly made part of another word, by pre-ceding it with a backslash (‘\’) or enclosing it in single (‘’’), double (‘"’) or backward (‘‘’) quotes. When not otherwise quoted a newline preceded by a ‘\’ is equivalent to a blank, but inside quotes this sequence results in a newline.
I believe that the issue is a function of the Shells and not 'sed'. Not sure that this is exactly what you are looking for but may help in some way. Cheers...
Robert