Shell Programming and Scripting

Hello,

I am curious. If I have a line of code run in bash

Code:

VAR="
It
is
a
nice
shiny
day
"

and I would like to be able to print this with the newlines in tact, is there a way? Are the newlines actually there but stripped by

Code:

echo $VAR

or

Code:

echo -e $VAR

?

In Python you can:

Code:

>>>VAR = """
Hello there
how are you
doing today
with things?
"""

>>>VAR
'Hello there\nHow are you\ndoing today\nwith things?\n'
>>>print (VAR)
Hello there
How are you
doing today
with things?

>>>

Notice that the newlines are actually present when displaying VAR in the interactive shell

I'm mainly using this concept to generate DOC strings for each function I'm writting. Each function adds to this DOC string. Currently, I'm hand-formatting with

Code:

DOC="function [-a]\n\ndoes so and so\n\n-a\tdoes what arg -a is supposed to do

then running

Code:

echo -e $DOC

when I want to print this.

I'd love to be able to:

Code:

DOC="
function [-a]

does so and so

-a(tab goes here but web editor won't let me) does what arg -a is supposed to do)

note: returns 0 if successful returns 1 if not
"
echo $DOC

and have this print this to screen with newlines.

I would like to get for variables what you can get with the below for generating files.

Code:

cat > $SOURCELIST << EOF
$REPO
$SRC
EOF

vs

Code:

echo -e "${REPO}\n${SRC}" > $SOURCELIST

to put a .list file in /etc/apt/sources.list.d for example

For a more complex example, this:

Code:

cat > print_hello_then_ls_a_dir << EOF
#! /bin/bash
#

echo -e "\n\nHello world.\n\nHow are you today?
ls /etc/apt
EOF

is much easier than

Code:

echo -e "#! /bin/bash\n#\n\necho -e \"\\\n\\\nHello world.\\\n\\\nHow are you today?\"\nls /etc/apt" > print_hello_then_ls_a_dir

There's got to be a similar trick for creating variables and echoing them short of making a bunch of /tmp files and then cat'ing them using a similar technique as above (and IMHO makes the code much more readable)

Could someone please point me in the right direction?

Am I just asking too much from the shell?

With thanks,
Narnie

set the IFS field to newline
Eg:-
OIFS=$IFS
IFS=:

replace : with new line


HTH,
PL

The newlines are in the value of VAR, but after the shell substitutes VAR's value, the resulting string is split into words. The characters in the value of the IFS (internal field separator) variable -- which defaults to space, tab, newline -- determine which characters delimit words. So, your newlines are used to split the string into words which are then passed to echo as its arguments. What you see is the end result is echo doing its job, which is to print each of those words separated by a space and followed by a newline.

Solution: Wrap the variable in double quotes to prevent the word splitting step from occurring.

Code:

echo "$VAR"

Regards,
alister

Wow! I feel pretty stupid now. Why didn't I think about quoting? Works like a charm. Can't wait to use this in new apps!"

Also, I' will try daptal's approach as well.

Thanks both for replying.

Happy New Year,
Narnie

By the way, Narnie, unless you want the shell to expand variables and do command substitution insde your python function docstrings, use single quotes to ensure that all characters within it are taken literally. The only caveat being that you need to replace occurrences of ' with '\'' to get them in (this closes the single quoted string, backslash escapes a single quoted string, then reopens the single quoted string ... if you get that then you got shell quoting down ).

Code:

DOC='
function docstring with embedded newlines and
embedded '\''single quotes'\'' works fine without
accidentally expanding something that looks to the shell like
a $var or a command $(rm importantfile)'

echo "$DOC"

Using double quotes for assigning to DOC would have caused the shell to expand $var (if unset, a null string would have taken its place) and remove importantfile. I mention this just in case.

Happy New Year to you as well.

Take care,
alister