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Exec command behaviour

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# 1  
Old 02-26-2013
Lightbulb Exec command behaviour
Hello All,

I came across this line in a shell script that I was looking at yesterday. Couldn't get a clue of what it does. Smilie

Code:
....
....
blah blah
....
.....

exec >&- 2>&-

......
blah blah
.....

Can someone explain me this??

Usually I have seen exec commands used to redirect std output and error output to log files. And this one is different! Smilie
# 2  
Old 02-26-2013
Looks like that program is closing stdout and stderr. C.f. man bash:
Quote:
Duplicating File Descriptors
The redirection operator
[n]<&word
is used to duplicate input file descriptors. If word expands to one or more digits, the file descriptor denoted by n is made to be
a copy of that file descriptor. If the digits in word do not specify a file descriptor open for input, a redirection error occurs.
If word evaluates to -, file descriptor n is closed. If n is not specified, the standard input (file descriptor 0) is used.
The operator
[n]>&word
is used similarly to duplicate output file descriptors . . .
# 3  
Old 02-26-2013
So RudiC,

I have this
Code:
exec >file1 2>&1
cmd1
cmd2
cmd3
exec >&- 2> &-
cmd4
cmd5

By your explanation, file1 will have the outputs of cmd1, cmd2 & cmd3.
Then exec >&- 2>&- will stop redirecting to file1. Thus outputs of cmd4 & cmd5 will be directed to stdout & stderr.

Is my understanding correct?

---------- Post updated at 03:12 PM ---------- Previous update was at 03:12 PM ----------

So RudiC,

I have this
Code:
exec >file1 2>&1
cmd1
cmd2
cmd3
exec >&- @> &-
cmd4
cmd5

By your explanation, file1 will have the outputs of cmd1, cmd2 & cmd3.
Then exec >&- 2>&- will stop redirecting to file1. Thus outputs of cmd4 & cmd5 will be directed to stdout & stderr.

Is my understanding correct?
# 4  
Old 02-26-2013
No, it closes stdout and stderr entirely - your shell won't have any output channel any more.
This User Gave Thanks to RudiC For This Post:
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