cut command fields

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1
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I noticed these two different fields behaviors using cut command:

bash:~$ var=`cat /proc/cpuinfo | grep 'model name' | uniq | cut -d ' ' -f 3,4,5,6,7,8 ` 
echo $var

outputs

Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz

and:

bash:~$ echo `cat /proc/cpuinfo | grep 'model name' | uniq` | cut -d ' ' -f 3,4,5,6,7,8

outputs

: Intel(R) Core(TM) i7-3632QM CPU @

fields numbers are the same but different outputs. Why?

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

add a commentÂ |Â

up vote
1
down vote

favorite

I noticed these two different fields behaviors using cut command:

bash:~$ var=`cat /proc/cpuinfo | grep 'model name' | uniq | cut -d ' ' -f 3,4,5,6,7,8 ` 
echo $var

outputs

Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz

and:

bash:~$ echo `cat /proc/cpuinfo | grep 'model name' | uniq` | cut -d ' ' -f 3,4,5,6,7,8

outputs

: Intel(R) Core(TM) i7-3632QM CPU @

fields numbers are the same but different outputs. Why?

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

add a commentÂ |Â

up vote
1
down vote

favorite

I noticed these two different fields behaviors using cut command:

bash:~$ var=`cat /proc/cpuinfo | grep 'model name' | uniq | cut -d ' ' -f 3,4,5,6,7,8 ` 
echo $var

outputs

Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz

and:

bash:~$ echo `cat /proc/cpuinfo | grep 'model name' | uniq` | cut -d ' ' -f 3,4,5,6,7,8

outputs

: Intel(R) Core(TM) i7-3632QM CPU @

fields numbers are the same but different outputs. Why?

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

I noticed these two different fields behaviors using cut command:

bash:~$ var=`cat /proc/cpuinfo | grep 'model name' | uniq | cut -d ' ' -f 3,4,5,6,7,8 ` 
echo $var

outputs

Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz

and:

bash:~$ echo `cat /proc/cpuinfo | grep 'model name' | uniq` | cut -d ' ' -f 3,4,5,6,7,8

outputs

: Intel(R) Core(TM) i7-3632QM CPU @

fields numbers are the same but different outputs. Why?

grep cut command-substitution uniq

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

edited 5 mins ago

Jeff Schaller

34.9k952115

edited 5 mins ago

Jeff Schaller

34.9k952115

edited 5 mins ago

Jeff Schaller

34.9k952115

asked 1 hour ago

pietro letti

8117

asked 1 hour ago

pietro letti

8117

asked 1 hour ago

pietro letti

8117

add a commentÂ |Â

1 Answer
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up vote
3
down vote

It is because the unquoted `` backquote command substitution has removed an extra space between the model name and the : characters. Refer to the outputs without the grep to see the difference for yourself

echo `cat /proc/cpuinfo | grep 'model name' | uniq`
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz

and with

cat /proc/cpuinfo | grep 'model name' | uniq
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
# ^^ - 2 spaces rather than one

As a result the cut sees different fields from number 3 onwards in both the cases. This can be fixed if you avoid using backticks and use $(..) with a proper quoted substitution

echo "$(cat /proc/cpuinfo | grep 'model name' | uniq)" | cut -d ' ' -f 3,4,5,6,7,8

But that said, using cat/grep etc sequentially can be avoided and a single awk can be used in-place of it

awk -F: '$1 ~ "model name" print $2 ' /proc/cpuinfo

Or even more exact, if a single leading space in the above result is worrisome, remove it using sub

awk -F: '$1 ~ "model name" sub(/^[[:space:]]/ ,"" , $2); print $2 ' /proc/cpuinfo

Or if you have GNU variant of grep which has PCRE regex enabled, which you can use as

grep -oP 'model name(s+):(s+)K(.+)' /proc/cpuinfo

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

add a commentÂ |Â

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1 Answer
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1 Answer
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active

oldest

votes

up vote
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down vote

echo `cat /proc/cpuinfo | grep 'model name' | uniq`
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz

and with

cat /proc/cpuinfo | grep 'model name' | uniq
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
# ^^ - 2 spaces rather than one

As a result the cut sees different fields from number 3 onwards in both the cases. This can be fixed if you avoid using backticks and use $(..) with a proper quoted substitution

echo "$(cat /proc/cpuinfo | grep 'model name' | uniq)" | cut -d ' ' -f 3,4,5,6,7,8

But that said, using cat/grep etc sequentially can be avoided and a single awk can be used in-place of it

awk -F: '$1 ~ "model name" print $2 ' /proc/cpuinfo

Or even more exact, if a single leading space in the above result is worrisome, remove it using sub

awk -F: '$1 ~ "model name" sub(/^[[:space:]]/ ,"" , $2); print $2 ' /proc/cpuinfo

Or if you have GNU variant of grep which has PCRE regex enabled, which you can use as

grep -oP 'model name(s+):(s+)K(.+)' /proc/cpuinfo

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

add a commentÂ |Â

up vote
3
down vote

echo `cat /proc/cpuinfo | grep 'model name' | uniq`
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz

and with

cat /proc/cpuinfo | grep 'model name' | uniq
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
# ^^ - 2 spaces rather than one

As a result the cut sees different fields from number 3 onwards in both the cases. This can be fixed if you avoid using backticks and use $(..) with a proper quoted substitution

echo "$(cat /proc/cpuinfo | grep 'model name' | uniq)" | cut -d ' ' -f 3,4,5,6,7,8

But that said, using cat/grep etc sequentially can be avoided and a single awk can be used in-place of it

awk -F: '$1 ~ "model name" print $2 ' /proc/cpuinfo

Or even more exact, if a single leading space in the above result is worrisome, remove it using sub

awk -F: '$1 ~ "model name" sub(/^[[:space:]]/ ,"" , $2); print $2 ' /proc/cpuinfo

Or if you have GNU variant of grep which has PCRE regex enabled, which you can use as

grep -oP 'model name(s+):(s+)K(.+)' /proc/cpuinfo

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

add a commentÂ |Â

up vote
3
down vote

echo `cat /proc/cpuinfo | grep 'model name' | uniq`
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz

and with

cat /proc/cpuinfo | grep 'model name' | uniq
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
# ^^ - 2 spaces rather than one

As a result the cut sees different fields from number 3 onwards in both the cases. This can be fixed if you avoid using backticks and use $(..) with a proper quoted substitution

echo "$(cat /proc/cpuinfo | grep 'model name' | uniq)" | cut -d ' ' -f 3,4,5,6,7,8

But that said, using cat/grep etc sequentially can be avoided and a single awk can be used in-place of it

awk -F: '$1 ~ "model name" print $2 ' /proc/cpuinfo

Or even more exact, if a single leading space in the above result is worrisome, remove it using sub

awk -F: '$1 ~ "model name" sub(/^[[:space:]]/ ,"" , $2); print $2 ' /proc/cpuinfo

Or if you have GNU variant of grep which has PCRE regex enabled, which you can use as

grep -oP 'model name(s+):(s+)K(.+)' /proc/cpuinfo

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

echo `cat /proc/cpuinfo | grep 'model name' | uniq`
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz

and with

cat /proc/cpuinfo | grep 'model name' | uniq
model name : Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
# ^^ - 2 spaces rather than one

As a result the cut sees different fields from number 3 onwards in both the cases. This can be fixed if you avoid using backticks and use $(..) with a proper quoted substitution

echo "$(cat /proc/cpuinfo | grep 'model name' | uniq)" | cut -d ' ' -f 3,4,5,6,7,8

But that said, using cat/grep etc sequentially can be avoided and a single awk can be used in-place of it

awk -F: '$1 ~ "model name" print $2 ' /proc/cpuinfo

Or even more exact, if a single leading space in the above result is worrisome, remove it using sub

awk -F: '$1 ~ "model name" sub(/^[[:space:]]/ ,"" , $2); print $2 ' /proc/cpuinfo

Or if you have GNU variant of grep which has PCRE regex enabled, which you can use as

grep -oP 'model name(s+):(s+)K(.+)' /proc/cpuinfo

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

edited 37 mins ago

answered 53 mins ago

Inian

3,168822

answered 53 mins ago

Inian

3,168822

answered 53 mins ago

Inian

3,168822

add a commentÂ |Â

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