It was used as a workaround for bugs in older versions of the Bourne shell.
As far as I know, the buggy versions substituted "$@" with a single empty argument (instead of nothing) when no arguments were provided.
The ${1+"$@"} is evaluated as follows: if the first parameter is set, then substitute "$@", else nothing.
Ahhh... that's how it is. Thanks for the explanation.
I tried to look for it in 'parameter expansion' section of 'man bash', but on my machine (GNU bash, version 4.1.5) there is only
Code:
${parameter:+word}
, explained as:
Quote:
Use Alternate Value. If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted.
which is equivalent to what you say ${parameter+word} does. I tested the ${param+word} and ${param:+word} and the difference is in the case when 'param' is null:
Code:
$ cat doEcho.sh
#!/bin/bash
param=""
var=${param:+"Param has been set"}
echo Var: $var
$ ./doEcho.sh
Var:$ cat doEcho.sh
#!/bin/bash
param="blah"
var=${param:+"Param has been set"}
echo Var: $var
$ ./doEcho.sh
Var: Param has been set
No colon:
Code:
$ cat doEcho.sh
#!/bin/bash
param=""
var=${param+"Param has been set"}
echo Var: $var
$ ./doEcho.shVar: Param has been set$ cat doEcho.sh
#!/bin/bash
param="blah"
var=${param+"Param has been set"}
echo Var: $var
$ ./doEcho.sh
Var: Param has been set
With positional parameter, e.g. ${1+"word"}, the colon seems to make no difference.
Indeed, upon a better look, i found the colon documented in bash manual pages... my bad. Also positional params work, too. I guess I was hasty with my statements :-|
Thank you for corrections.
Hello.
System : opensuse leap 42.3
I have a bash script that build a text file.
I would like the last command doing :
print_cmd -o page-left=43 -o page-right=22 -o page-top=28 -o page-bottom=43 -o font=LatinModernMono12:regular:9 some_file.txt
where :
print_cmd ::= some printing... (1 Reply)
Hi Guys,
I'm sorry but I can't find answer for this, what is the meaning of -s option in "if" statement on unix scipting. Please see sample below:
opath=/home/output
for i in N1 N2 N3 N4
do
echo $i
if
then
grep $i $opath/N5_CRAI > $opath/N5_$i.crai
chmod 777 $opath/N5_$i.crai
... (7 Replies)
Hi, What means "##*", "% *" in a variable??
I have this in the script that i'm reading:
...
read line
echo $line
echo ${line#* }
echo ${line##* }
echo ${line% * }
...
The first print:
DN: RCROOT ONRM_ROOT_MO SNW ONRM_ROOT_MO BSC BSCCC2 BTS ALTOHATILLONOR
The second print:... (2 Replies)
Hi,
I have line in input file as below:
3G_CENTRAL;INDONESIA_(M)_TELKOMSEL;SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL
My expected output for line in the file must be :
"1-Radon1-cMOC_deg"|"LDIndex"|"3G_CENTRAL|INDONESIA_(M)_TELKOMSEL"|LAST|"SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL"
Can someone... (7 Replies)
I need to sort the following file by the rhdiskpower devices in the last column:
Total_MB Free_MB OS_MB Name Failgroup Library Label UDID Product Redund Path
1024 851 1024 OCRVOT1_0000 OCRVOT1_0000 System UNKNOWN ... (3 Replies)
Hi,
Could someone pls help me on the below command:
if
then
------------------
------------
fi
if
then
-------------
-------------------
-------------------
fi
What does this signify?
Thanks,
.. (4 Replies)
while (my $row = $sth->fetchrow_arrayref) {
$var->{"@$row"}=" ";
}
Can anyone help me understanding above mentioned.
i) As per my knowledge $row is taking ARRAY Refernce from the database
ii) @$row is containing the value of 0th index of the array, testted the same.
but I am not able... (0 Replies)
I ran 'diag' command to verify disk follow the below steps.
DIAG------?task selection-------ssa service aid-----Link verification
I found that there are 3 types of status. (Good, Failed and Power).
scp2: pdisk23 D69E584F 0 16 Power
scp2: pdisk19 D657E7A9 1 15 Power
scp2: pdisk28... (1 Reply)
05-22-2011
