stderr redirection by reading a file [duplicate]

up vote
2
down vote

favorite

This question already has an answer here:

How to make bash substitution $(<â€œfilenameâ€) silent

4 answers

I read content of the file into variable like this

var=$(<somefile)

But if the file doesn't exist I get accordingly an error message

bash: somefile: No such file or directory

Is it possible to redirect stderr to >/dev/null without using cat command?

asked Mar 14 at 8:37

renton

111

marked as duplicate by Jeff Schaller, Communityâ™¦ Mar 14 at 10:51

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a commentÂ |Â

up vote
2
down vote

favorite

This question already has an answer here:

How to make bash substitution $(<â€œfilenameâ€) silent

4 answers

I read content of the file into variable like this

var=$(<somefile)

But if the file doesn't exist I get accordingly an error message

bash: somefile: No such file or directory

Is it possible to redirect stderr to >/dev/null without using cat command?

asked Mar 14 at 8:37

renton

111

marked as duplicate by Jeff Schaller, Communityâ™¦ Mar 14 at 10:51

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a commentÂ |Â

up vote
2
down vote

favorite

This question already has an answer here:

How to make bash substitution $(<â€œfilenameâ€) silent

4 answers

I read content of the file into variable like this

var=$(<somefile)

But if the file doesn't exist I get accordingly an error message

bash: somefile: No such file or directory

Is it possible to redirect stderr to >/dev/null without using cat command?

asked Mar 14 at 8:37

renton

111

This question already has an answer here:

How to make bash substitution $(<â€œfilenameâ€) silent

4 answers

I read content of the file into variable like this

var=$(<somefile)

But if the file doesn't exist I get accordingly an error message

bash: somefile: No such file or directory

Is it possible to redirect stderr to >/dev/null without using cat command?

This question already has an answer here:

How to make bash substitution $(<â€œfilenameâ€) silent

4 answers

asked Mar 14 at 8:37

renton

111

asked Mar 14 at 8:37

renton

111

asked Mar 14 at 8:37

renton

111

asked Mar 14 at 8:37

renton

111

marked as duplicate by Jeff Schaller, Communityâ™¦ Mar 14 at 10:51

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by Jeff Schaller, Communityâ™¦ Mar 14 at 10:51

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a commentÂ |Â

2 Answers
2

active

oldest

votes

up vote
4
down vote

In this case, either use cat:

var=$( cat somefile 2>/dev/null )

or test for file existence first:

if [ -f somefile ]; then
 var=$(<somefile)
fi

To avoid the race condition in the last example (the file might theoretically disappear between the test and reading it):

if cp somefile myname 2>/dev/null; then
 var=$(<myname)
 rm -f myname
fi

The following will not work:

var=$(<somefile) 2>/dev/null
var=$(<somefile 2>/dev/null)

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

add a commentÂ |Â

up vote
2
down vote

You can use:

 var=$(<somefile); 2> /dev/null

answered Mar 14 at 10:22

StÃ©phane Chazelas

280k53515847

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

add a commentÂ |Â

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
4
down vote

In this case, either use cat:

var=$( cat somefile 2>/dev/null )

or test for file existence first:

if [ -f somefile ]; then
 var=$(<somefile)
fi

To avoid the race condition in the last example (the file might theoretically disappear between the test and reading it):

if cp somefile myname 2>/dev/null; then
 var=$(<myname)
 rm -f myname
fi

The following will not work:

var=$(<somefile) 2>/dev/null
var=$(<somefile 2>/dev/null)

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

add a commentÂ |Â

up vote
4
down vote

In this case, either use cat:

var=$( cat somefile 2>/dev/null )

or test for file existence first:

if [ -f somefile ]; then
 var=$(<somefile)
fi

To avoid the race condition in the last example (the file might theoretically disappear between the test and reading it):

if cp somefile myname 2>/dev/null; then
 var=$(<myname)
 rm -f myname
fi

The following will not work:

var=$(<somefile) 2>/dev/null
var=$(<somefile 2>/dev/null)

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

add a commentÂ |Â

up vote
4
down vote

In this case, either use cat:

var=$( cat somefile 2>/dev/null )

or test for file existence first:

if [ -f somefile ]; then
 var=$(<somefile)
fi

To avoid the race condition in the last example (the file might theoretically disappear between the test and reading it):

if cp somefile myname 2>/dev/null; then
 var=$(<myname)
 rm -f myname
fi

The following will not work:

var=$(<somefile) 2>/dev/null
var=$(<somefile 2>/dev/null)

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

In this case, either use cat:

var=$( cat somefile 2>/dev/null )

or test for file existence first:

if [ -f somefile ]; then
 var=$(<somefile)
fi

To avoid the race condition in the last example (the file might theoretically disappear between the test and reading it):

if cp somefile myname 2>/dev/null; then
 var=$(<myname)
 rm -f myname
fi

The following will not work:

var=$(<somefile) 2>/dev/null
var=$(<somefile 2>/dev/null)

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

edited Mar 14 at 10:05

answered Mar 14 at 8:48

Kusalananda

103k13201318

answered Mar 14 at 8:48

Kusalananda

103k13201318

answered Mar 14 at 8:48

Kusalananda

103k13201318

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

add a commentÂ |Â

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

This is the pettiest gripe, but the second fix has a race condition...
â€“Â Michael Homer
Mar 14 at 9:04

@MichaelHomer It has. The file might theoretically disappear between the test and reading it. Another way would be to copy the file and read it if that succeeded, but the cat is probably best (and also portable).
â€“Â Kusalananda
Mar 14 at 9:25

add a commentÂ |Â

up vote
2
down vote

You can use:

 var=$(<somefile); 2> /dev/null

answered Mar 14 at 10:22

280k53515847

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

add a commentÂ |Â

up vote
2
down vote

You can use:

 var=$(<somefile); 2> /dev/null

answered Mar 14 at 10:22

280k53515847

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

add a commentÂ |Â

up vote
2
down vote

You can use:

 var=$(<somefile); 2> /dev/null

answered Mar 14 at 10:22

280k53515847

You can use:

 var=$(<somefile); 2> /dev/null

answered Mar 14 at 10:22

280k53515847

answered Mar 14 at 10:22

280k53515847

answered Mar 14 at 10:22

280k53515847

answered Mar 14 at 10:22

280k53515847

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

add a commentÂ |Â

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

Hmm... yes, that would be best. Didn't we have this in an answer the other day (I can't find it)?
â€“Â Kusalananda
Mar 14 at 10:28

@Kusalananda, yes, I couldn't find it either, but I'm pretty sure there's a recent dup too.
â€“Â StÃ©phane Chazelas
Mar 14 at 10:35

add a commentÂ |Â

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