I have been trying to send parameter which also contains strong quoting but have been unsuccessful till now. I am trying to write a code something like this among with lots of variant which are also not working as expected :
diffFile()
{
cat dir1/$1 | "$2"
}
diffFile "chkconfig" "awk '{print $1}'"
But the problem is when i run the script the strong quoting gets escaped.
How can i pass the strong quoting?
Ok got a solution after playing with my script.
diffFile()
{
cat dir1/$1 | eval "$2"
}
diffFile "chkconfig" "awk '{print \$1}'"
Related
I have a script (I don't have edit access) which output whether the server is up or not. Essentially outputting either true or false.
How can I convert that output from lets say true to a key value pair like server_up=true or server_up=false. I tried using awk '{print $0} but didn't get very far. Not really sure how I can prepend string before it.
Thanks for any insights team!
If the output is only true or false, for one server, you can assign it directly to a variable.
server_up=$( prog.sh some arg list )
If you need that as a k=v pair,
printf "server_up=%s\n" $( prog.sh some arg list )
Obviously you have to run the program itself to get the output, but there's no need for an awk.
If you just want to use awk,
prog.sh your args | awk '{ print "server_up="$0 }'
or sed,
prog.sh your args | sed 's/^/server_up=/'
if there might be spaces to clean up, then
prog.sh your args | sed 's/^ */server_up=/'
or
prog.sh your args | sed -E 's/^\s*(\S+)\s*$/server_up=\1/'
Just output the variable with = in front of it then.
printf server_up=
prog.sh your args
Using the builtin read command with ProcSub
#!/usr/bin/env bash
read -r value < <(script_that_generates_the_output)
server_up=$value
To answer this:
How can I convert that output from lets say true to a key value pair like server_up=true or server_up=false.
#!/usr/bin/env bash
read -r value < <(script_that_generates_the_output)
case "$value" in
true) server_up=true;;
false) server_up=false;;
esac
The case statement is most probably superfluous though.
I want to write a script for any name given as an argument and prints the list of paths
to home directories of people with the name.
I am new at scripts. Is there any simple way to do this with awk or egrep command?
Example:
$ show names jakub anna (as an argument)
/home/users/jakubo
/home/students/j_luczka
/home/students/kubeusz
/home/students/jakub5z
/home/students/qwertinx
/home/users/lazinska
/home/students/annalaz
Here is the my friend's code but I have to write it from a different way and it has to be simple like this code
#!/bin/bash
for name in $#
do
awk -v n="$name" -F ':' 'BEGIN{IGNORECASE=1};$5~n{print $6}' /etc/passwd | while read line
do
echo $line
done
done
Possible to use a simple awk script to look for matching names.
The list of names can be passed as a space separated list to awk, which will construct (in the BEGIN section) a combined pattern (e.g. '(names|jakub|anna)'). The pattern is used for testing the user name column ($5) of the password file.
#! /bin/sh
awk -v "L=$*" -F: '
BEGIN {
name_pat = "(" gensub(" ", "|", "g", L) ")"
}
$5 ~ name_pat { print $6 }
' /etc/passwd
Since at present the question as a whole is unclear, this is more of a long comment, and only a partial answer.
There is one easy simplification, since the sample code includes:
... | while read line
do
echo $line
done
All of the code shown above after and including the | is needless, and does nothing, (like a UUoC), and should therefore be removed. (Actually echo $line with an unquoted $line would remove formatting and repeated spaces, but that's not relevant to the task at hand, so we can say the code above does nothing.)
I've written my first script, one in which I want to know if 2 files have the same values in a specific column.
Both files are WEKA machine-learning prediction outputs for different algorithms, hence they have to be in the same format, but the prediction column would be different.
Here's the code I've written based on the tutorial presented in https://linuxconfig.org/bash-scripting-tutorial-for-beginners:
#!/bin/bash
lineasdel1=$(wc -l $1 | awk '{print $1}')
lineasdel2=$(wc -l $2 | awk '{print $1}')
if [ "$lineasdel1" != "$lineasdel2" ]; then
echo "Files $1 and $2 have different number of lines, unable to perform"
exit 1
fi
function quitalineasraras {
awk '$1!="==="&&NF>0'
}
function acomodo {
awk '{gsub(/^ +| +$/, ""); gsub(/ +0/, " W 0"); gsub(/ +1$/, " W 1"); gsub(/ +/, "\t") gsub(/\+\tW/, "+"); print}'
}
function procesodel1 {
quitalineasraras "$1" | acomodo
}
function procesodel2 {
quitalineasraras "$2" | acomodo
}
el1procesado=$(procesodel1)
el2procesado=$(procesodel2)
function pegar {
paste <(echo "$el1procesado") <(echo "$el2procesado")
}
function contarintersec {
awk 'BEGIN {FS="\t"} $3==$8 {n++} END {print n}'
}
unido=$(pegar)
interseccion=$(contarintersec $unido)
echo "Estos 2 archivos tienen $interseccion coincidencias."
I ran all individual codes of all functions in the terminal and verified they work successfully (I'm using Linux Mint 19.2). Script's permissions also have been changed to make it executable. Paste command also is supposed to work with that variable syntax.
But when I run it via:
./script.sh file1 file2
if both files have the same number of lines, and I press enter, no output is obtained; instead, the terminal opens an empty line with cursor waiting for something. In order to write another command, I've got to press CTRL+C.
If both files have different number of lines the error message prints successfully, so I think the problem has something to do with the functions, with the fact that awk has different syntax for some chores, or with turning the output of functions into variables.
I know that I'm missing something, but can't come up with what could be.
Any help will be appreciated.
what could be.
function quitalineasraras {
awk '$1!="==="&&NF>0'
}
function procesodel1 {
quitalineasraras "$1" | acomodo
}
el1procesado=$(procesodel1)
The positional variables $1 are set for each function separately. The "$1" inside procesodel1 expands to empty. The quitalineasraras is passed one empty argument "".
The awk inside quitalineasraras is passed only the script without the filename, so it reads the input for standard input, ie. it waits for the input on standard input.
The awk inside quitalineasraras without any file arguments makes your script seem to wait.
I am searching an event field in a file but is giving wrong output. I am searching gpio-keys event in input devices for which I have written a script, but I'm unable to print anything in output file (in my case I am writing in a button device file it is null always). Please help me to figure out this. Where am I doing wrong in script file?
Bash script:
#!/bin/bash
if grep -q "gpio-keys" /proc/bus/input/devices ; then
EVENT=$(cat /proc/bus/input/devices | grep "Handlers=kbd")
foo= `echo $EVENT | awk '{for(i=1;i<=NF;i++) if($i=="evbug")printf($(i-1))}'`
#foo=${EVENT:(-7)}
echo -n $foo > /home/ubuntu/Setups/buttonDevice
fi
i am still not able to get anything in buttondevce
That's no wonder, since in the input line
H: Handlers=kbd event0
there's nowhere the evbug your awk script is looking for.
I my case it is event0 but it may vary also depends on how kernel allows.
If it is event0 or similar, then it's nonsensical to look for evbug. Change the statement
if($i=="evbug")printf($(i-1))
to
if ($i~"event") print $i
(using regular expression match).
I have rewritten my script like above. but through it, I have got two events(event0, event3) but … my input devices are many but i want the gpio-keys event
Aha - in order to take only the handler line from the gpio-keys section, you can use sed with an address range:
EVENT=`sed -n '/gpio-keys/,/Handlers=kbd/s/.*Handlers=kbd //p' </proc/bus/input/devices`
Prakash, I don't have access to your google drive. But I just want to give you some suggestion:-
foo= `echo $EVENT | awk '{for(i=1;i<=NF;i++) if($i=="evbug")printf($(i-1))}'`
This is old style now. Better use like below:-
foo=$(echo $EVENT | awk '{for(i=1;i<=NF;i++) if($i=="evbug")printf($(i-1))}')
Also always use double quotes "" when echoing a variable. See below:-
echo -n "$foo" > /home/ubuntu/Setups/buttonDevice
Try with the below code it will work for you
#!/bin/bash
if grep "gpio-keys" /proc/bus/input/devices >/dev/null ; then
cat /proc/bus/input/devices | grep "Handlers=kbd" | awk '{for(i=1;i<=NF;i++){ if($i ~ /eve/){printf "%s \n", $i} } }') > /home/ubuntu/Setups/buttonDevice
fi
The output in buttonDevice would be
event0
event1
.
.
.
.
event100
Is there any way to modify a shell variable inside awk block of code?
--------- [shell_awk.sh]---------------------
#!/bin/bash
shell_variable_1=<value A>
shell_variable_2=<value B>
shell_variable_3=<value C>
awk 'function A(X)
{ return X+1 }
{ a=A('$shell_variable_1')
b=A('$shell_variable_2')
c=A('$shell_variable_3')
shell_variable_1=a
shell_variable_2=b
shell_variable_3=c
}' FILE.TXT
--------- [shell_awk.sh]---------------------
This is a very simple example, the real script load a file and make some changes using functions, I need to keep each value before change into a specific variable, so then I can register into MySQL the before and after value.
The after value is received from parameters ($1, $2 and so on).
The value before I already know how to get it from the file.
All is done well, except the shell_variable been set by awk variable. Outside from awk block code is easy to set, but inside, is it possible?
No program -- in awk, shell, or any other language -- can directly modify a parent process's memory. That includes variables. However, of course, your awk can write contents to stdout, and the parent shell can read that content and modify its own variables itself.
Here's an example of awk that writes key/value pairs out to be read by bash. It's not perfect -- read the caveats below.
#!/bin/bash
shell_variable_1=10
shell_variable_2=20
shell_variable_3=30
run_awk() {
awk -v shell_variable_1="$shell_variable_1" \
-v shell_variable_2="$shell_variable_2" \
-v shell_variable_3="$shell_variable_3" '
function A(X) { return X+1 }
{ a=A(shell_variable_1)
b=A(shell_variable_2)
c=A(shell_variable_3) }
END {
print "shell_variable_1=" a
print "shell_variable_2=" b
print "shell_variable_3=" c
}' <<<""
}
while IFS="=" read -r key value; do
printf -v "$key" '%s' "$value"
done < <(run_awk)
for var in shell_variable_{1,2,3}; do
printf 'New value for %s is %s\n' "$var" "${!var}"
done
Advantages
Doesn't use eval. Content such as $(rm -rf ~) in the output from awk won't be executed by your shell.
Disadvantages
Can't handle variable contents with newlines. (You could fix this by NUL-delimiting output from your awk script, and adding -d '' to the read command).
A hostile awk script could modify PATH, LD_LIBRARY_PATH, or other security-sensitive variables. (You could fix this by reading variables into an associative array, rather than the global namespace, or by enforcing a prefix on their names).
The code above uses several ksh extensions also available in bash; however, it will not run with POSIX sh. Thus, be sure not to run this via sh scriptname (which only guarantees POSIX functionality).