shell scipting: append output of a command to a variable

jonhewer · 08-24-2005, 03:08 AM

hi

doing a little bit of shell scripting.....

it's possible to append the output of a command to a file:

eg. echo "hello" >> file

but is there an equivalent to append the output to a variable? (i'm building up a log message which i want to both write to a log file and email)

the only way i currently know how to do this is:

var=${var}`echo "hello"`

thanks for your help
jon

slackie1000 · 08-24-2005, 03:41 AM

hi there,

Code:

var=`echo "Hello World"`

won't work?
regards
slackie1000

jonhewer · 08-24-2005, 03:48 AM

Quote:

Originally posted by slackie1000
hi there,

Code:

var=`echo "Hello World"`

won't work?
regards
slackie1000

works for me....

slackie1000 · 08-24-2005, 04:31 AM

hi there,
so, if it works... what is your question?

i thought, you want to have the output of a command assigned to a variable.
regards,
slackie1000

jonhewer · 08-24-2005, 04:34 AM

i want to append the output to a variable, ie. keeping its existing value, and appending the new data

var=${var}`echo "hello"` will do it, but i was wondering whether there's a cleaner way using the >> operator maybe?

theYinYeti · 08-24-2005, 05:04 AM

I know two methods:
1/ You don't need a line break:

Code:

var="${var}$(/path/to/command params)"

2/ You need a line break:

Code:

var="$(echo "$var"; /path/to/command params)"

Yves.

jonhewer · 08-24-2005, 05:09 AM

thanks theYinYeti that second method is handy

is it possible to append the stderr of a command to a variable?

theYinYeti · 08-24-2005, 05:33 AM

Of course. Instead of writing:
/path/to/command params

you write:
/path/to/command params 2>&1
if you want both stdout and stderr,

/path/to/command params 2>&1 >/dev/null
if you only want stderr.

Yves.

jonhewer · 08-24-2005, 05:36 AM

ah of course, cheers

slackie1000 · 08-24-2005, 05:41 AM

*slackie1000 hits his head in the wall and buys an english dictionary*
sorry mate...
my mistake..
regards,
slackie1000

jonhewer · 08-24-2005, 05:42 AM

lol, no worries