Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: meaning of ${1+"$@"}
Top Forums Shell Programming and Scripting meaning of ${1+"$@"} Post 302524187 by mirni on Sunday 22nd of May 2011 06:22:06 AM
Old 05-22-2011
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.sh
Var: 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.
Last edited by mirni; 05-22-2011 at 08:31 AM..
 

9 More Discussions You Might Find Interesting

1. AIX

What's meaning of "POWER" in diag command.?

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)
Discussion started by: pattarapongn
1 Replies

2. UNIX for Dummies Questions & Answers

Meaning of $var->{"@$row[0]"}=" "; ???

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)
Discussion started by: jaigs_27
0 Replies

3. Shell Programming and Scripting

Meaning of "if [ -x /opt/OV/bin/ovpolicy ]"

Hi, Could someone pls help me on the below command: if then ------------------ ------------ fi if then ------------- ------------------- ------------------- fi What does this signify? Thanks, .. (4 Replies)
Discussion started by: ww26683
4 Replies

4. UNIX for Dummies Questions & Answers

the meaning of "!:*" in "alias foo 'command\!:*' filename"

Hi: How can I remove my own post? Thanks. (2 Replies)
Discussion started by: phil518
2 Replies

5. Shell Programming and Scripting

Meaning of "b" modifier in "sort" command

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)
Discussion started by: wjssj
3 Replies

6. Shell Programming and Scripting

awk command to replace ";" with "|" and ""|" at diferent places in line of file

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)
Discussion started by: shis100
7 Replies

7. UNIX for Dummies Questions & Answers

Variable "##*", "% *" meaning

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)
Discussion started by: darocham
2 Replies

8. UNIX for Dummies Questions & Answers

What is the meaning of "-s" option in "if" statement?

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)
Discussion started by: rymnd_12345
7 Replies

9. Shell Programming and Scripting

Bash script - Print an ascii file using specific font "Latin Modern Mono 12" "regular" "9"

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)
Discussion started by: jcdole
1 Replies

LEARN ABOUT DEBIAN

colorgccrc

COLORGCCRC(5)							File Formats Manual						     COLORGCCRC(5)

NAME

       colorgccrc - configuration file for colorgcc

DESCRIPTION

       A colorgccrc configuration file is used to configure the highlighting of the compiler output from colorgcc.

SYNTAX

       Each  line  consists  of  a  keyword  designating  a configuration variable.  The keyword is followed by `:' and then one or several values
       (depending on the keyword).  Lines beginning with a hash mark `#' are comments.

CONFIGURATION VARIABLES

       g++ | gcc | c++ | cc | g77 | gcj | gnat | gpc
	      Specifies the paths to the compilers.  Takes one value; a path to the compiler.

       nocolor
	      Specifies what terminal types colorization should be disabled on.  Takes one or several values, separated by whitespace.

       srcColor
	      Specifies the highlighting attributes source-code should be given.  Takes one or several color attributes.  See  the  section  COLOR
	      ATTRIBUTES for more information.

       introColor
	      Specifies  the  highlighting  attributes	for normal compiler output.  Takes one or several color attributes.  See the section COLOR
	      ATTRIBUTES for more information.

       warningFileNameColor | errorFileNameColor
	      Specifies the highlighting attributes for the filename in a  warning  or	an  error,  respectively.   Takes  one	or  several  color
	      attributes.  See the section COLOR ATTRIBUTES for more information.

       warningNumberColor | errorNumberColor
	      Specifies  the  highlighting  attributes	for  the  line-number  in a warning or an error, respectively.	Takes one or several color
	      attributes.  See the section COLOR ATTRIBUTES for more information.

       warningMessageColor | errorMessageColor
	      Specifies the highlighting attributes for the message-text in a warning or an error,  respectively.   Takes  one	or  several  color
	      attributes.  See the section COLOR ATTRIBUTES for more information.

COLOR ATTRIBUTES

       The following attributes are valid for highlighting.

       clear, reset

       bold, underline, underscore, blink, reverse, concealed

       black, red, green, yellow, blue, magenta, cyan, white

       on_black, on_red, on_green, on_yellow, on_blue, on_magenta, on_cyan, on_white

SEE ALSO

       gcc(1), colorgcc(1)

HISTORY

       Jan 15 2003: Initial version of this manual-page.

REPORTING BUGS

       Report bugs to <jmoyers@geeks.com>

AUTHORS

       Jamie Moyers <jmoyers@geeks.com> is the author of colorgcc.

       This  manual  page  was	written  by Joe Wreschnig <piman@sacredchao.net>, and modified by David Weinehall <tao@debian.org>, for the Debian
       GNU/Linux system (but may be used by others).

COPYRIGHT

       Copyright (C) 2003 Jamie Moyers
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

								   Jan 15, 2003 						     COLORGCCRC(5)
All times are GMT -4. The time now is 06:07 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy