Execute command (function) from a variable in a script

So, I want to create a script where I check sth from a website. I have a text file with different websites in it and I want to check all websites simultaneously. To do this I'm creating a command step by step in a variable calling a function which will check every website. This is my code:

checkWebsite(){

    WEBSITE="$2"

    echo "Parameter is $WEBSITE"

}



COUNTER=0;



input=websites.txt



myCommand=()

while IFS= read -r line

do

    if [[ "$line" != "#"* ]]; #ignoring comments if there are any

    then

        myCommand[COUNTER]="checkWebsite $line"

        COUNTER=$((COUNTER + 1))

        myCommand[COUNTER]=" & "

        COUNTER=$((COUNTER + 1))

    fi

done < "$input"



unset 'myCommand[${#myCommand[@]}-1]' #deleting the last " & "



echo "MY COMMAND: "

echo ${myCommand[@]}

echo " "



echo ${myCommand[0]}

checkWebsite ${myCommand[0]}

"${myCommand[0]}"

These are the results:
results

As you can see, if I call the function from the script everything is ok but if I call the function from the variable it doesn't work. I understand why this is happening(it's like I run that command from the terminal) but I don't know how can I make it run the function from the script when I execute the command from the variable. Does anyone know how can I make that happen?

Thanks in advance

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

Putting it in a variable makes it harder and messier than it has to be. Is there a reason why you're not just running it directly?

– that other guy
Nov 24 '18 at 20:08

Asked and answered a lot of times: bash command parameter substitution site:stackoverflow.com. Which would you like as your duplicate?

– jww
Nov 24 '18 at 20:17

Also see BashFAQ #50. "${myCommand[0]}" entirely defeats the whole purpose of using an array -- dereffing just the first element means it's just another string.

– Charles Duffy
Nov 24 '18 at 20:19

BTW, declare -p myCommand gives you a much more accurate idea of your array's contents than echo ${myCommand[@]} does. (For that matter, printf '%qn' "${myCommand[@]}" would be an improvement as well).

– Charles Duffy
Nov 25 '18 at 0:39

add a comment |

checkWebsite(){

    WEBSITE="$2"

    echo "Parameter is $WEBSITE"

}



COUNTER=0;



input=websites.txt



myCommand=()

while IFS= read -r line

do

    if [[ "$line" != "#"* ]]; #ignoring comments if there are any

    then

        myCommand[COUNTER]="checkWebsite $line"

        COUNTER=$((COUNTER + 1))

        myCommand[COUNTER]=" & "

        COUNTER=$((COUNTER + 1))

    fi

done < "$input"



unset 'myCommand[${#myCommand[@]}-1]' #deleting the last " & "



echo "MY COMMAND: "

echo ${myCommand[@]}

echo " "



echo ${myCommand[0]}

checkWebsite ${myCommand[0]}

"${myCommand[0]}"

These are the results:
results

Thanks in advance

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

Putting it in a variable makes it harder and messier than it has to be. Is there a reason why you're not just running it directly?

– that other guy
Nov 24 '18 at 20:08

Asked and answered a lot of times: bash command parameter substitution site:stackoverflow.com. Which would you like as your duplicate?

– jww
Nov 24 '18 at 20:17

Also see BashFAQ #50. "${myCommand[0]}" entirely defeats the whole purpose of using an array -- dereffing just the first element means it's just another string.

– Charles Duffy
Nov 24 '18 at 20:19

BTW, declare -p myCommand gives you a much more accurate idea of your array's contents than echo ${myCommand[@]} does. (For that matter, printf '%qn' "${myCommand[@]}" would be an improvement as well).

– Charles Duffy
Nov 25 '18 at 0:39

add a comment |

checkWebsite(){

    WEBSITE="$2"

    echo "Parameter is $WEBSITE"

}



COUNTER=0;



input=websites.txt



myCommand=()

while IFS= read -r line

do

    if [[ "$line" != "#"* ]]; #ignoring comments if there are any

    then

        myCommand[COUNTER]="checkWebsite $line"

        COUNTER=$((COUNTER + 1))

        myCommand[COUNTER]=" & "

        COUNTER=$((COUNTER + 1))

    fi

done < "$input"



unset 'myCommand[${#myCommand[@]}-1]' #deleting the last " & "



echo "MY COMMAND: "

echo ${myCommand[@]}

echo " "



echo ${myCommand[0]}

checkWebsite ${myCommand[0]}

"${myCommand[0]}"

These are the results:
results

Thanks in advance

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

checkWebsite(){

    WEBSITE="$2"

    echo "Parameter is $WEBSITE"

}



COUNTER=0;



input=websites.txt



myCommand=()

while IFS= read -r line

do

    if [[ "$line" != "#"* ]]; #ignoring comments if there are any

    then

        myCommand[COUNTER]="checkWebsite $line"

        COUNTER=$((COUNTER + 1))

        myCommand[COUNTER]=" & "

        COUNTER=$((COUNTER + 1))

    fi

done < "$input"



unset 'myCommand[${#myCommand[@]}-1]' #deleting the last " & "



echo "MY COMMAND: "

echo ${myCommand[@]}

echo " "



echo ${myCommand[0]}

checkWebsite ${myCommand[0]}

"${myCommand[0]}"

These are the results:
results

Thanks in advance

linux bash shell terminal sh

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

edited Nov 24 '18 at 20:15

jww

52.8k39224492

edited Nov 24 '18 at 20:15

jww

52.8k39224492

edited Nov 24 '18 at 20:15

jww

52.8k39224492

asked Nov 24 '18 at 19:35

Savvas Th

154

asked Nov 24 '18 at 19:35

Savvas Th

154

asked Nov 24 '18 at 19:35

Savvas Th

154

Putting it in a variable makes it harder and messier than it has to be. Is there a reason why you're not just running it directly?

– that other guy
Nov 24 '18 at 20:08

Asked and answered a lot of times: bash command parameter substitution site:stackoverflow.com. Which would you like as your duplicate?

– jww
Nov 24 '18 at 20:17

Also see BashFAQ #50. "${myCommand[0]}" entirely defeats the whole purpose of using an array -- dereffing just the first element means it's just another string.

– Charles Duffy
Nov 24 '18 at 20:19

BTW, declare -p myCommand gives you a much more accurate idea of your array's contents than echo ${myCommand[@]} does. (For that matter, printf '%qn' "${myCommand[@]}" would be an improvement as well).

– Charles Duffy
Nov 25 '18 at 0:39

add a comment |

Putting it in a variable makes it harder and messier than it has to be. Is there a reason why you're not just running it directly?

– that other guy
Nov 24 '18 at 20:08

Asked and answered a lot of times: bash command parameter substitution site:stackoverflow.com. Which would you like as your duplicate?

– jww
Nov 24 '18 at 20:17

Also see BashFAQ #50. "${myCommand[0]}" entirely defeats the whole purpose of using an array -- dereffing just the first element means it's just another string.

– Charles Duffy
Nov 24 '18 at 20:19

BTW, declare -p myCommand gives you a much more accurate idea of your array's contents than echo ${myCommand[@]} does. (For that matter, printf '%qn' "${myCommand[@]}" would be an improvement as well).

– Charles Duffy
Nov 25 '18 at 0:39

Putting it in a variable makes it harder and messier than it has to be. Is there a reason why you're not just running it directly?

– that other guy
Nov 24 '18 at 20:08

Asked and answered a lot of times: bash command parameter substitution site:stackoverflow.com. Which would you like as your duplicate?

– jww
Nov 24 '18 at 20:17

Also see BashFAQ #50. "${myCommand[0]}" entirely defeats the whole purpose of using an array -- dereffing just the first element means it's just another string.

– Charles Duffy
Nov 24 '18 at 20:19

BTW, declare -p myCommand gives you a much more accurate idea of your array's contents than echo ${myCommand[@]} does. (For that matter, printf '%qn' "${myCommand[@]}" would be an improvement as well).

– Charles Duffy
Nov 25 '18 at 0:39

add a comment |

1 Answer
1

active

oldest

votes

Don't use an array here. It causes a lot of trouble and adds no value whatsoever. Instead, start your background tasks inside the loop:

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || checkWebsite "$line" &

done < "$input"

If you really want an array, populate it from the loop, and -- again -- start items individually without it.

websites=( )

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || websites+=( "$line" )

done < "$input"



for site in "${websites[@]}"; do

  checkWebsite "$site" &

done

Why doesn't the other approach work? Because & only acts as a command separator when parsed as syntax, and parameter expansion results are data, not syntax.

You would need to use eval to make your expansion results parse as syntax; unless done with great care, this would cause serious security vulnerabilities.

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

Don't use an array here. It causes a lot of trouble and adds no value whatsoever. Instead, start your background tasks inside the loop:

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || checkWebsite "$line" &

done < "$input"

If you really want an array, populate it from the loop, and -- again -- start items individually without it.

websites=( )

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || websites+=( "$line" )

done < "$input"



for site in "${websites[@]}"; do

  checkWebsite "$site" &

done

Why doesn't the other approach work? Because & only acts as a command separator when parsed as syntax, and parameter expansion results are data, not syntax.

You would need to use eval to make your expansion results parse as syntax; unless done with great care, this would cause serious security vulnerabilities.

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

add a comment |

Don't use an array here. It causes a lot of trouble and adds no value whatsoever. Instead, start your background tasks inside the loop:

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || checkWebsite "$line" &

done < "$input"

If you really want an array, populate it from the loop, and -- again -- start items individually without it.

websites=( )

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || websites+=( "$line" )

done < "$input"



for site in "${websites[@]}"; do

  checkWebsite "$site" &

done

Why doesn't the other approach work? Because & only acts as a command separator when parsed as syntax, and parameter expansion results are data, not syntax.

You would need to use eval to make your expansion results parse as syntax; unless done with great care, this would cause serious security vulnerabilities.

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

add a comment |

Don't use an array here. It causes a lot of trouble and adds no value whatsoever. Instead, start your background tasks inside the loop:

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || checkWebsite "$line" &

done < "$input"

If you really want an array, populate it from the loop, and -- again -- start items individually without it.

websites=( )

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || websites+=( "$line" )

done < "$input"



for site in "${websites[@]}"; do

  checkWebsite "$site" &

done

Why doesn't the other approach work? Because & only acts as a command separator when parsed as syntax, and parameter expansion results are data, not syntax.

You would need to use eval to make your expansion results parse as syntax; unless done with great care, this would cause serious security vulnerabilities.

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

Don't use an array here. It causes a lot of trouble and adds no value whatsoever. Instead, start your background tasks inside the loop:

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || checkWebsite "$line" &

done < "$input"

If you really want an array, populate it from the loop, and -- again -- start items individually without it.

websites=( )

while IFS= read -r line; do

  [[ "$line" = "#"* ]] || websites+=( "$line" )

done < "$input"



for site in "${websites[@]}"; do

  checkWebsite "$site" &

done

Why doesn't the other approach work? Because & only acts as a command separator when parsed as syntax, and parameter expansion results are data, not syntax.

You would need to use eval to make your expansion results parse as syntax; unless done with great care, this would cause serious security vulnerabilities.

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

answered Nov 24 '18 at 20:21

Charles Duffy

174k25197252

add a comment |

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