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Bash: What does “masking return values” mean?

5

shellcheck generated the following warning

SC2155: Declare and assign separately to avoid masking return

values

For this line of code

local key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

What does "masking return values" mean, and how does it pertain to the aforementioned warning?

bash shell-script shellcheck

share|improve this question

edited 53 mins ago

Inquisitor

asked 1 hour ago

InquisitorInquisitor

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5

shellcheck generated the following warning

SC2155: Declare and assign separately to avoid masking return

values

For this line of code

local key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

What does "masking return values" mean, and how does it pertain to the aforementioned warning?

bash shell-script shellcheck

share|improve this question

edited 53 mins ago

Inquisitor

asked 1 hour ago

InquisitorInquisitor

304

New contributor

Inquisitor is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

shellcheck generated the following warning

SC2155: Declare and assign separately to avoid masking return

values

For this line of code

local key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

What does "masking return values" mean, and how does it pertain to the aforementioned warning?

bash shell-script shellcheck

share|improve this question

edited 53 mins ago

Inquisitor

asked 1 hour ago

InquisitorInquisitor

304

New contributor

Inquisitor is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

SC2155: Declare and assign separately to avoid masking return

values

local key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

share|improve this question

edited 53 mins ago

Inquisitor

asked 1 hour ago

InquisitorInquisitor

304

New contributor

Inquisitor is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 53 mins ago

Inquisitor

asked 1 hour ago

InquisitorInquisitor

304

New contributor

Inquisitor is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 1 hour ago

InquisitorInquisitor

304

New contributor

Inquisitor is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 1 hour ago

InquisitorInquisitor

304

1 Answer
1

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oldest

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5

When you declare a variable as either local or exported that in itself is a command that will return success or not.

$ var=$(false)

$ echo $?

1

$ export var=$(false)

$ echo $?

0

So if you wanted to act on the return value of your command (echo "$current_line" | mawk '/.+=.+/ {print $1 }'), you would be unable to since it's going to exit with 0 as long as the local declaration succeeds (which is almost always will).

In order to avoid this it suggests declaring separately and then assigning:

local key_value

key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

This is a shellcheck rule I frequently ignore and IMO is safe to ignore as long as you know you aren't trying to act on the return value of that variable declaration.

You can ignore it by adding the following to the top of your script (Below the hashbang of course):

# shellcheck disable=SC2155

share|improve this answer

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

add a comment | 

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5

When you declare a variable as either local or exported that in itself is a command that will return success or not.

$ var=$(false)

$ echo $?

1

$ export var=$(false)

$ echo $?

0

So if you wanted to act on the return value of your command (echo "$current_line" | mawk '/.+=.+/ {print $1 }'), you would be unable to since it's going to exit with 0 as long as the local declaration succeeds (which is almost always will).

In order to avoid this it suggests declaring separately and then assigning:

local key_value

key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

This is a shellcheck rule I frequently ignore and IMO is safe to ignore as long as you know you aren't trying to act on the return value of that variable declaration.

You can ignore it by adding the following to the top of your script (Below the hashbang of course):

# shellcheck disable=SC2155

share|improve this answer

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

add a comment | 

5

When you declare a variable as either local or exported that in itself is a command that will return success or not.

$ var=$(false)

$ echo $?

1

$ export var=$(false)

$ echo $?

0

So if you wanted to act on the return value of your command (echo "$current_line" | mawk '/.+=.+/ {print $1 }'), you would be unable to since it's going to exit with 0 as long as the local declaration succeeds (which is almost always will).

In order to avoid this it suggests declaring separately and then assigning:

local key_value

key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

This is a shellcheck rule I frequently ignore and IMO is safe to ignore as long as you know you aren't trying to act on the return value of that variable declaration.

You can ignore it by adding the following to the top of your script (Below the hashbang of course):

# shellcheck disable=SC2155

share|improve this answer

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

add a comment | 

When you declare a variable as either local or exported that in itself is a command that will return success or not.

$ var=$(false)

$ echo $?

1

$ export var=$(false)

$ echo $?

0

So if you wanted to act on the return value of your command (echo "$current_line" | mawk '/.+=.+/ {print $1 }'), you would be unable to since it's going to exit with 0 as long as the local declaration succeeds (which is almost always will).

In order to avoid this it suggests declaring separately and then assigning:

local key_value

key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

This is a shellcheck rule I frequently ignore and IMO is safe to ignore as long as you know you aren't trying to act on the return value of that variable declaration.

You can ignore it by adding the following to the top of your script (Below the hashbang of course):

# shellcheck disable=SC2155

share|improve this answer

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

$ var=$(false)

$ echo $?

1

$ export var=$(false)

$ echo $?

0

local key_value

key_value=$(echo "$current_line" | mawk '/.+=.+/ {print $1 }')

# shellcheck disable=SC2155

share|improve this answer

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

answered 1 hour ago

Jesse_bJesse_b

13.4k23370

answered 1 hour ago

Jesse_bJesse_b

13.4k23370