[bug-gawk] feature request: expanding escape sequences

[Ed Morton]

Guys - I just tried to do something conceptually trivial and discovered there is 
literally NO good way to do it in awk so I was wondering if a gawk function 
could be provided to do it?

I just want to be able to expand escape sequences in text read 
from an input file. For example, let's say I have:

    $ cat file
    a\tb
    c\td

and I want to output:

    a<tab>b
    c<tab>d

where "<tab>" is a literal control character.

The most concise solution I've come up with is 
to invoke the shell to parse the file, e.g.

    $ awk '{ system("printf \047" $0 "\n\047") }' file
    a       b
    c       d

but that has some caveats, not least of which is that if the input file contains 
text like '$(ls)' then that command will be executed!

The alternatives seem to be writing text to manually parse each line to convert 
every escape-char to it's literal character, or using a script to read the input 
file to generate another script and then execute that.

I'm not looking for an `eval` function, just something that will convert escape 
sequences to their equivalent characters so I can do something like this if 
`file` contains lines of formatting text:

    awk '{ printf expandEscapes($0), "whatever" }' file

and expandEscapes() will just return it's argument as a string with all escape 
chars expanded (actual function name up for grabs of course).

What do you think?

     Ed.