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I am trying to write a shell script in the form of an executable file that echoes yes if I pass an argument that is valid variable name or no if it is not a valid variable name.
So for example ./valid abc would return yes and ./valid 123 would return no
As of right now, no matter what I write, I get yes a response. Also, form what I have learned so far, is that variable names cannot start with a number, which is why ./valid 123 should return no
This is the code I have so far:
name="$1"
if test "$name"=[a-zA-Z]+[a-zA-Z0-9_]*
then
echo "yes"
else
echo "no"
fi
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In shell scripting Suppose I have a file name called aaa_djdidm_cjcjcj_20220602.txt
I only want the name except the date.
Expected result - aaa_djdidm_cjcjcj
If you want to remove the part after the last _:
NAME="aaa_djdidm_cjcjcj_20220602.txt"
NEW_NAME=${NAME%_*}
The % operator is useful do remove the motif (here _*) of a named parameter (here NAME)
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add=+
echo "$((1{$add}2))"
If I write 1+2 it outputs 3, but when I store the + sign in a variable called "add" and then use it in place of + operator, it just outputs it as if it was a string. How can I use the variable and still make it output 3?
As far as I can see, the code is wrong and should not print anything but an error.
What you should do is write the variable as ${add}, not {$add}.
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I'm try to make a script for checking some ethx.
If the eth is up and connected my script is working
When its not working I have a problem.
RESD=$(ssh -q vmx#$1 cat /sys/class/net/$3/dormant)
I get in RESD the following result:
cat: /sys/class/net/eth3/dormant: Invalid argument
I want to put in RESD now the first letter.
How can I do this?
Thanks
As per the comment above, this what you want to do: RESD=${RESD:0:1}? This is pure bash equivalent of RESD=$(echo $RESD | cut -c1).
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What method can one use to alternate a variable which is dependable by time?
For example, this week var = Office, then next week var = Oncall?
The resulting script will be using crontab to output the contents of var depending on which week it was.
Thanks.
You can use date +%W to check what week number of the year it is (starting Monday).
You can alternate between the two with e.g.
if (( $(date +%W) % 2 ))
then
var=Office
else
var=Oncall
fi
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I have a unix assignment and What I have isnt working right. It doesnt format like the normal "cal" function.
#!/bin/bash
d=`date '+%Y'`;
$((++d));
calstr=`cal $d`;
echo $calstr;
You don't need the $ in line 2, and you need to wrap the $calstr in double quotes:
#!/bin/bash
d=`date '+%Y'`;
((++d));
calstr=`cal $d`;
echo "$calstr";