The parameter tag has no wiki summary.
24
votes
3answers
6k views
How to pass parameters to an alias?
For bash script, I can use "$@" to access arguments. What's the equivalent when I use an alias?
12
votes
1answer
471 views
How do ${0##*/} and ${0%/*} work?
I'm quite confused about the following regular expressions I found in a shell script:
${0##*/}
${0%/*}
How do they work?
12
votes
2answers
1k views
How to safely pass variables to root-enabled scripts?
This question is totally general and not only applicable to my situation, but... I have a small busybox appliance where I want a non-root user to be able to execute a particular script with root ...
12
votes
0answers
353 views
Should I use $* or $@? [duplicate]
Which one of $* or $@ is better to use (in array syntax,command line parameters, etc.) to avoid any bugs/problems in code? Or it does not make any difference?
11
votes
2answers
1k views
What does `:-` mean in a shell script
I saw this in the end of an awesome shell script but I can't understand the login here because I think it's being short-handed for a longer command.
spark ${@:-`cat`}
This apears at the end of this ...
8
votes
1answer
12k views
How to check if there are no parameters provided to a command?
How do you check if $* is empty? In other words, how to check if there were no arguments provided to a command?
8
votes
1answer
6k views
How to display kernel command line parameters?
In the grub.conf configuration file I can specify command line parameters that the kernel will use, i.e.:
kernel /boot/kernel-3-2-1-gentoo root=/dev/sda1 vga=791
After booting a given kernel, is ...
7
votes
5answers
2k views
Indexing and modifying Bash parameter array $@
Is it possible to refer to indexes in $@? I can't find any reference to use like the following anywhere in GrayCat's wiki, and the Advanced Scripting Guide and others assign this to a different ...
7
votes
3answers
6k views
How do I split the $0 variable to find directory and relative paths in bash?
The $0 variable contains the path info of the script.
How can I change the path info to absolute path? I mean how to process ~, ., .. or similar?
How can I split the path info into directory and ...
5
votes
4answers
478 views
How can I create a empty file whose name begins with a dash? [duplicate]
How can we create a empty file with the unix name -stuff.
It means the name start with -. I tried with touch -stuff but it didn't work.
5
votes
2answers
199 views
Is it possible to use shell parameter variables ($1, …, $@) directly in CLI?
Sometimes it is necessary to emulate and verify the above variables in small examples and then can be copied immediately to some script, etc.
I tried to solve by using a simple example in the ...
5
votes
3answers
3k views
Print shell arguments in reverse order
I am a bit stuck. My task is to print the arguments to my script in reverse order except the third and fourth.
What I have is this code:
#!/bin/bash
i=$#
for arg in "$@"
do
case $i
in
...
5
votes
3answers
2k views
Transform an array into arguments of a command?
I have an array of "options" of a command.
my_array=(option1 option2 option3)
I want to call this command in a bash script, using the values from array as options. So, command $(some magic here ...
4
votes
2answers
159 views
Why is $# always 0 in my function?
Bash is driving me nuts. I can't figure out why the following (nor any of the dozens of variations I've literally copied and pasted from examples) fails to work:
#!/bin/bash
echo $#
function main {
...
4
votes
2answers
543 views
Documentation of kernel parameters
Where can I find a technical description of the kernel parameters listed in /proc/sys (ob Linux)?
4
votes
2answers
389 views
Passing parsed output of sed to find (in this direction)
Well, I think you can find dozens of questions on this platform how to pipe find output to sed, but I haven't found anything for the reverse direction so far. What I want to do is modify my input, and ...
4
votes
1answer
336 views
Writing command synopsis in standard man format
I am writing a script and in the usage() function I want to specify the usage.
My script uses either option1 or option2 or both. One of them is mandatory.
Is there a standard way to write it up?
4
votes
3answers
853 views
How to tell of whether the kernel parameter [passed at command line] is a valid kernel parameter?
In the grub.conf configuration file I can specify command line parameters that the kernel will use, i.e.:
kernel /boot/kernel-3-2-1-gentoo root=/dev/sda1 vga=791 plasticDuck
After booting up a ...
4
votes
1answer
144 views
Use boot parameter to perform certain actions after boot
I'm asking myself if I can use Grub 2 to tell the Operating System which actions to perform after boot.
Background:
I have a HTPC with Debian Wheezy installed. Sometimes I want to use the System as a ...
4
votes
2answers
258 views
Function caller positional parameters
I need to read and write the positional parameters $@ of a function's caller. The Bash man page says that:
A shell function is an object that is called like a simple command and
executes a ...
3
votes
2answers
256 views
$BASHPID And $$ differ in some cases
I'm reading "BASH pocket guide of Oreilly".
It said:
The process ID of the current Bash process.
In some cases, this can differ from $$.
Above explanation , explained $BASHPID variable.
...
3
votes
1answer
42 views
Customize bash to always include a certain parameter
When using the "ls" command, bash prints in the following format:
file1 file2 file3 file4
file5 file6 file7 file8
But when given the parameter "-1", it prints:
file1
file2
file3
etc...
Is there ...
3
votes
3answers
2k views
How to pass a string parameter on bash function?
I have this code that does work:
get_parameter ()
{
echo "$query" | sed -n 's/^.*name=\([^&]*\).*$/\1/p' | sed "s/%20/ /g"
}
But I want to replace the "name" with the parameter that I pass ...
3
votes
2answers
1k views
How to escape < or > in a parameter in shell?
I'd like to use grep with a PCRE expression that contains the < character. Bash thinks I want to redirect, but I don't want to. How can I escape <?
3
votes
2answers
225 views
how to make getopts just read the first character post `-`
I have a shell script testShell.sh which uses getopts as below:
#!/bin/bash
while getopts ":j:e:" option; do
case "$option" in
j) MYHOSTNAME=$OPTARG ;;
e) SCRIPT_PATH=$OPTARG ;;
...
3
votes
1answer
165 views
How can I pipe a path to pushd?
This seems like it should be easy enough to do, but I'm clearly not understanding something fundamental about piping output back and forth.
I'm trying to do something like this:
bundle show ...
3
votes
2answers
509 views
Getopts option processing, Is it possible to add a non hyphenated [FILE]?
I'm using getopts for all of my scripts that require advanced option parsing, and It's worked great with dash. I'm familiar with the standard basic getopts usage, consisting of [-x] and [-x OPTION]. ...
3
votes
1answer
223 views
How to unset the positional parameters?
How do I do this:
set foo bar baz
unset # Something else here
echo $# # Should ouput 0
By doing set "", $# will still be 1 and not 0.
3
votes
2answers
153 views
Should stdin or filenames be discarded if both are provided?
grep and sed ignore stdin if you provide a filename parameter:
$ echo foo > test.txt
$ echo foobar | grep f test.txt
foo
$ echo foobar | sed -e 's/foo/bar/' test.txt
bar
Is this established ...
2
votes
2answers
126 views
Parameter splitting
I have a bash script that is a simple wrapper around another process:
$ cat ~/bin/s3cmd
#!/bin/sh
trickle -u 80 ~/bin/s3cmd.py $*
$
This works great when the parameters don't contain spaces. ...
2
votes
3answers
125 views
Why are POSIX Find Parameters Different from Other Program styles?
Why is a parameter in the POSIX find command added with a single hyphen for multi-character parameter names, while most other programs use single hyphen to indicate multiple single-character flags, ...
2
votes
4answers
231 views
How to write a very simple wrapper that provides default parameters?
Given a program that requires some parameters, e.g. program -in file.in -out file.out, what would be the simple-most approach to write a bash script that could be called with or without any of these ...
2
votes
2answers
1k views
How do I echo just 1 column of output from ls command?
Lets say when I do ls command the output is:
file1 file2 file3 file4
Is it possible to display only a certain column of output, in this case file2? I have tried the following with no success:
echo ...
2
votes
1answer
85 views
How to manipulate all parameters of a shell script at once?
While for a finite amount of parameters one can explicitly do something like
wrapped_function "${1#prefix}" "${2#prefix}" "${3#prefix}" # etc.,
isn't there a simpler way to manipulate all ...
2
votes
2answers
610 views
what does Curl's stand-alone hyphen (-) mean?
what's the stand-alone hyphen (between the -C & -O) stand for in this command?
curl -C - -O http://www.intersil.com/content/dam/Intersil/documents/fn67/fn6742.pdf
FWIW- I'm following a ...
2
votes
2answers
87 views
What is the bash syntax for extracting the values from multiple instances of the same argument?
I want to use multiple instances of command line paramater such as the -d option used by PHP for passing PHP options. I am currently using the getopts command in bash.
With PHP invocation it would ...
2
votes
2answers
299 views
Want a seperate file to store mysql username, password, and database name
I have as script that dumps a mysql database, and compresses the file. What I want to do is have another (edit) file which can change the username, password and database name. Then somehow connecting ...
2
votes
1answer
138 views
Bash: slice of positional parameters
How can I get a slice of $@ in Bash without first having to copy all positional parameters to another array like this?
argv=($@)
echo ${argv[@]:2};
2
votes
2answers
86 views
Parameter expansion seems to be missing a piece
I'm currently learning how to write simple scripts and can't get my head around a very simple problem.
I have the following command in my script...
touch ${DIRECTORY}/${FILE}
This command appears ...
2
votes
5answers
653 views
Where are command line arguments (e.g. 'some.text') actually passed to?
From what I know, parameters you pass to a command, goes to it's STDIN stream.
so this:
cut -d. -f2 'some.text'
should be perfectly identical to this:
echo 'some.text' | cut -d. -f2
as we send ...
2
votes
3answers
265 views
How to substitute awk argument?
I want simplify awk command for common usage so instead of writing awk '{print "rm -r"$4 }' each time I want to write myawk "rm -r"$4.
I've tried to write such function
myawk() { awk '{ print $1 }' ...
2
votes
1answer
125 views
prevent trap from altering underscore variable $_
I have the following code in my bashrc to get the execution time of the last command from http://stackoverflow.com/a/1862762
function timer_start {
timer=${timer:-$SECONDS}
}
function timer_stop {
...
2
votes
2answers
991 views
GRUB2 and kernel vga= parameter
According to the documentation, use of the vga= kernel parameter is deprecated as of GRUB2. The fact that some newer kernels don't seem to support it anymore on certain adapters is of no concern as ...
1
vote
1answer
371 views
Is it possible to use a parameter within an alias command [duplicate]
Possible Duplicate:
How to pass parameters to an alias?
As answered in Can less retain colored output? I want to use git diff --color=always filename | less -r to get a colored output of my ...
1
vote
2answers
282 views
Transforming positional arguments of a shell script
I'm trying to write a shell script that will transform positional
arguments that are passed to it as follows.
The shell script passes these arguments to a binary executable
(ffigen) which is derived ...
1
vote
1answer
112 views
What's the right way to set Linux kernel runtime parameters?
What's the prescribed way to set Linux kernel runtime parameters? I've seen sometimes that people will set these in files such as /etc/rc.local.
Is this really the right way to do this?
1
vote
1answer
149 views
Execute command supplied by function parameters
I'm trying to create a function method in a bash script that executes a command which is supplied to the method by the paramters.
Meaning somethings like this:
special_execute()
{
# Some code
...
1
vote
1answer
467 views
Passing Command Line Arguments to java From JPackage Script
I installed Rachota -- a time tracking program written in Java -- from the Fedora repo, and yum installed the rachota.jar file to /usr/share/java, but it also created a script at /usr/bin/rachota. ...
1
vote
1answer
365 views
Permanently set kernel parameters [isolcpus] without grub?
Is there any way to set kernel parameters in an Ubuntu-based system without relying on grub? (not available in the target environment)
Specifically I want to set the isolcpus parameter to dedicate ...
0
votes
1answer
109 views
How can I pass in a parameter to sed?
To be more precise - how can I pass in a parameter to a program that then calls sed - how can I 'pass' that parameter along?
I have a file 'source_code.sc'.
I have a sed script "find_expect":
#n
...
