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This is an assignment I received.
I have been requested to explain what the purpose of this code is. However, when I execute this, there does not appear any output.
As I am new to shell scripting, could somebody help me out?
Thanks a lot.
#!/bin/bash
# $1 = node IP
# $2 = node port
# $3 = hostname to resolve
[[ $# != 3 ]] && logger -p local0.error -t ${0##*/} -- "usage: ${0##*/} <node IP> <node port> <hostname to resolve>" && exit 1
node_ip=$(echo $1 | sed 's/::ffff://')
dig +short #$node_ip $3 IN A &> /dev/null
[[ $? == 0 ]] && echo “UP”
$#: number of parameters passed to your script, if you execute this script like this: bash filename.sh p1 p2 p3 p4, the $# in the filename.sh will be evaluated to 4
$?: return value of the previous command. In shell, return value of non-zero means something wrong happened.
[[ $# != 3 ]] && logger ... && 1: means if the amount of parameters is not 3, then log something and exit with return value 1
node_ip=$(echo $1 | sed 's/::ffff://'): replace the ::ffff: in the first parameter and assign it to node_ip
dig +short #$node_ip $3 IN A &> /dev/null: call dig command and redirect the output to /dev/null, so you can't see any thing printed out. By the way, I don't know what dig does
[[ $? == 0 ]] && echo “UP”: if dig command (namely the previous command) returns a zero value, which means SUCCESS, then print the word UP
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cat a.sh
#!/bin/bash
t=1232
echo $1
#echo $t
when i run the script "./a.sh $t" I can't get value 1232
when the script replacement with echo $t ,run the script "./a.sh" can get vaule 1232
can anybody else tell me ,if i use "./a.sh $t" this form ,how can get the vaule,thanks alot
have no ideas to get the variables throug the termi
When you run "./a.sh $t your current shell evaluates $t to '' so $1 is unset in your script and it will just execute echo.
If you quote the the variable either ./a.sh \$t or ./a.sh '$t' your script will do echo '$t'. You can then use either eval to get it to evaluate the expression:
eval echo "$1"
or preferable strip off the leading '$' and use indirect variable:
var=${1:1}
echo "${!var}"
If you just need to store data use json or sqlite instead of a script.
If you have logic in your script consider just passing in the variable names and if not set dump all variables (using the name convention that your variables are lower case):
#!/bin/bash
if [ -z "$1" ]
then
set | grep "^[a-z]"
exit 0
fi
for v in "$#"
do
set | grep "^$v="
done
and you then do:
$ ./a t
t=1232
$ ./a
t=1232
I think your variable t are out of scope. Therefore, what you want to do is assign the variable t=1232, beforehand, and use it as an argument. So the script would be
#!/bin/bash
echo $1
Then call the script as you wanted to with variable t already assigned to the value, so it would print the desired output
t=1232
./script.sh $t
I think that's that. would love to hear your thoughts tho
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So I have a shell script called "concat" that currently takes command line arguments and prints the contents of files named on the command line. I need to now create a script called "concatconvert" that calls the "concat" script, takes the contents of files and converts them.
The following is the code of my script "concat":
#!/bin/bash
if [ $# -eq 0 ]; then
printf "Usage: concat FILE ... \nDescription: Concatenates FILE(s)
to standard output separating them with divider -----.\n" >&2
exit 1
fi
for var in "$#"
do
if [[ ! -e "$var" ]]; then
printf "One or more files does not exist\n" >$2
exit 1
fi
done
for var in "$#"
do
if [ -f "$var" ]; then
cat $var
printf -- "-----\n"
fi
done
exit 0
I am going to be calling "concat" using
#!/bin/bash
./concat
in the concatconvert script.
Concatconvert is going to take arguments "-u" and "-l"
Ultimately the script would be executed as:
./concatconvert -u test1.txt test2.txt
-u converts contents of files to uppercase.
For example, "This is a test" becomes "THIS IS A TEST".
-l converts contents of files to lowercase.
For example, "This is a test" becomes "this is a test".
Only one option can be provided at a time.
I am not too sure where to begin on this. I appreciate any help.
You should use tr command as mentioned by #jenesaisquoi.
The tr command in UNIX is a command-line utility for translating or
deleting characters.
To use it to change everything to lower case command would be :
echo "This is Test" | tr [:upper:] [:lower:]
this is test
To use it to change everything to upper case command would be :
echo "This is Test" | tr [:lower:] [:upper:]
THIS IS TEST
To use it for a file use below command :
tr '[:upper:]' '[:lower:]' < filename
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hi can someone help me with this.
How to Write a script that takes in as argument a filename and displays its modification date and time in this way exactly :
[user#localhost...]$ bash script.sh temp.txt
the file temp.txt was modified on May 1 20:20
And then modify that script in such a way that it lists the modification dates for directories whose names contain a given pattern in this way exactly :
[user#local....]$ bash script.sh testRegex Pub
the file testRegex was modified on May 1 20:22
the directory /home/user/Public was modified on Dec 26 08:00
the directory /home/user/Pubs. was modified on May 2 20:00
please help I need to answer this fast
Thanks
This is pretty simple to do actually. You should read up on the stat command as #John Bollinger said. I also used the date command to format the date. You can read up on taking arguments for a script here
Combining all of this would give -
#!/bin/bash
filename=$1;
dirname=$2;
file_mod_date=`date -d #$( stat -c %Y $1 ) +%m" "%B" "%H:%M`;
echo "The file ${filename} was modified on ${file_mod_date}";
if [ "$2" == "" ]; then
exit 1;
else
for i in /home/user/*${dirname}*/; do
dir_mod_date=`date -d #$( stat -c %Y $i ) +%m" "%B" "%H:%M`;
echo "The directory ${i} was modified on ${dir_mod_date}";
done
fi
A good way to do this is with passing options and values:
For example:
file_name=""
help_message="To use this script type script.sh --file /path/to/file.txt"
# -- Get input options (if any)
while [[ $# > 0 ]] ;do
key="$1"
case ${key,,} in
-f|--file)
file_name="${2,,}"
shift
;;
-h|--help)
echo -e "$help_message"
exit;
shift
;;
esac
shift
done
Call the script like this:
bash script.sh -f "temp.txt"
With regard to the "logic" of the script, you will have to figure that out ;-)
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I have following code in a shell script. It is all working fine.
#!/bin/bash
baseDirPath = '/stackoverflow/question'
newDir = '/stackoverflow/question/answers'
# first check some business condition
if [[ some condition here ]]
then
# check if base Directory path already exit
if [ -d $baseDirPath ];then
# check if new Directory exits or not, if not create one
if [ ! -d $newDir ];then
mkdir $newDir
if [ $? -ne 0 ] ; then
echo "error occurred while creating directory "
fi
fi
else
exit 1;
fi
fi
This is very confusing and not very clean code i feel.
I am very new to programming so not sure how it can be clean.
I am very curious if it can be made simpler or there is some other way to do this.
(The complete shell script is not shown above, just the complicated if-else part is illustrated.)
#!/bin/bash
die(){ >&2 printf '%s\n' "$#"; exit 1; }
#Can't have spaces here
baseDirPath='/stackoverflow/question'
newDir='/stackoverflow/question/answers'
# first check some business condition
if [ some condition here ]; then
# check if base Directory path already exit
mkdir -p "$newDir" || die 'error occured while creating directory'
fi
This changes the semantics slightly--it exits if the creation of newDirs fails for whatever reasons -- baseDirPath is not a directory or baseDirPath is a directory and newDir cannot be created.
You can probably get rid of that error message too. mkdir will already give you an error on stderr if it fails for some reason:
mkdir -p "$newDir" || exit 1
If most of your commands should work like this (i.e., either succeed or bring down the whole script), then you're probably better off setting set -e (~ exit when a command returns with a nonzero status) and then just doing:
mkdir -p "$newDir"
This can be pretty thoroughly simplified:
#!/bin/bash
baseDirPath='/stackoverflow/question'
newDir='/stackoverflow/question/answers'
# first check some business condition
if [[ some condition here ]]; then
if ! mkdir -p "${newDir}"; then
echo "Unable to create directory ${newDir}. Aborting."
exit 1
fi
# Proceed as normal
fi
If you really do need for the baseDirPath to exist, then that can certainly be added as a condition:
if [[ ! -d "${baseDirPath}" ]] || ! mkdir -p "${newDir}"; then
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I want to create if statement, but in this statement are some errors
for i in ${#:2} ; do
if (( $2 -eq $i ))
then
continue
fi
done
How to fix my if statement
Your statement only works for integers.
If you want to compare them as strings, you can use [[ "string1" = "string2" ]]:
$ cat -v myscript
#!/bin/bash
for i in "${#:2}" ; do
if [[ "$2" = "$i" ]]
then
echo "$2 and $i are the same"
else
echo "$2 and $i are different"
fi
done
$ chmod +x myscript
$ ./myscript dummy target foo bar target
target and target are the same
target and foo are different
target and bar are different
target and target are the same
As you can see from this runnable example, it works. If you find that it doesn't on your system, you should provide a complete example like the above demonstrating it.
I would suggest
if [ "$2" = "$i" ]