Why isn't tilde expansion performed on the input to read?

up vote
4
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

add a comment |

up vote
4
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

add a comment |

up vote
4
down vote

favorite

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

Why has tilde expansion not occurred in the output of this script?

#!/bin/bash



read -p "Enter filename: " fname

if [[ -d $fname ]]

then

        echo "$fname is a directory"

else

        echo "$fname is not a directory"

fi

Output:

$ bash -x test_cd.sh 

+ read -p 'Enter filename: ' fname

Enter filename: ~/Music

+ [[ -d ~/Music ]]

+ echo ' ~/Music is not a directory'

 ~/Music is not a directory

command-line bash scripts

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

edited yesterday

Zanna

48.9k13123234

edited yesterday

Zanna

48.9k13123234

edited yesterday

Zanna

48.9k13123234

asked yesterday

jestadi

234

New contributor

asked yesterday

jestadi

234

asked yesterday

jestadi

234

New contributor

jestadi 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 |

1 Answer
1

active

oldest

votes

up vote
5
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited yesterday

answered yesterday

dessert

21k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
5
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited yesterday

answered yesterday

dessert

21k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

add a comment |

up vote
5
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited yesterday

answered yesterday

dessert

21k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

add a comment |

up vote
5
down vote

accepted

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited yesterday

answered yesterday

dessert

21k55896

That’s simply because read doesn’t perform tilde expansion before saving the string, neither is it performed on a variable content later. You can use $HOME instead and enter

$HOME/Music

or let the script test for ~/ and replace it (taken from this answer):

case "$fname" in "~/"*)

  fname="${HOME}/${x#"~/"}"

esac

You can also use bash Parameter Expansion to replace ~/ with $HOME at the beginning of the string:

if [[ -d ${fname/#~//$HOME/} ]]

This variable is expanded before the substitution is performed.

edited yesterday

answered yesterday

dessert

21k55896

edited yesterday

answered yesterday

dessert

21k55896

answered yesterday

dessert

21k55896

answered yesterday

dessert

21k55896

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

add a comment |

1

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

And also because it's not required nowhere in POSIX standard, and as consequence nowhere in bash manual. +1
– Sergiy Kolodyazhnyy
yesterday

@SergiyKolodyazhnyy what do you mean? What is not mentioned? Tilde expansion is mentioned. Do you mean tilde expansion in the input to read?
– Zanna
yesterday

@Zanna Tilde expansion is not mentioned in the read description in both POSIX and bash manuals. What's not in the manual is just as important as what's in it :)
– Sergiy Kolodyazhnyy
yesterday

add a comment |

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