Bash - sed multiple commands in single line
Bash - sed multiple commands in single line
Playing with sed - the commands below do what's required but one liners would be better. I have tried combining the first two commands (with a separating ';') to remove the trailing ':' without success. Otherwise, resorted to removing the last ':' and writing to a new file to perform the next operation.
File 'sys' with a single line containing a variable number characters and ':' separator. For example;
Input - 'sys' first line 3.000000:50: desired output, two variables thd=3 mem=50
3.000000:50:
thd=3 mem=50
thd=$(echo | sed 's/.......:.*//' < sys)
sed 's/:$//' < sys > sys1
mem=$(echo | sed 's|........:||' < sys1)
Is there a way to combine the first two sed commands to avoid writing a second file? I have tried this various ways
Something like this - EDIT: this is the wrong order to remove the trailing ':'
thd=$(echo | sed 's/:$//;s/.......:.*//' < sys)
mem=$(echo | sed 's|........:||' < sys1)
Output 3 50: with the separator attached.
3 50:
EDIT: This is the correct order and produces the desired output. Bash does not save the result of the first operation in the file sys. Which I should have picked up in the 3 liner.
thd=$(echo | sed 's/.......:.*//' < sys)
mem=$(echo | sed 's|........:||;s/:$//' < sys)
I have modified the question...
– GeorgeC
Aug 28 at 9:56
2 Answers
2
If you need two variables to be assigned values independently, the first containing the number before the point and the second the number between the colons, you can use an approach like
thd=$(cut -f1 -d. < sys)
mem=$(cut -f2 -d: < sys)
Assigning both at the same time is also possible:
read thd mem < <(tr "." ":" < sys | cut -f1,3 -d: --output-delimiter=" ")
The cut version is ideal. Just a few characters.
– GeorgeC
Aug 28 at 15:38
the read version requires the
tr -d option. Still couldn't get it to work on my system.– GeorgeC
Aug 29 at 8:13
tr -d
If you use the
-d option of tr, you will delete the separators and lose the information needed for proper field separation.– Poshi
Aug 29 at 8:48
-d
tr
As you say
-d doesn't work - this does read thd mem < <(cut -f1,2 -d: --output-delimiter=" " < sys) if happy to accept the trailing .000000, which makes no difference in my application - no need for the tr options in that case.– GeorgeC
Aug 29 at 11:25
-d
read thd mem < <(cut -f1,2 -d: --output-delimiter=" " < sys)
.000000
tr
Try this:
$ echo '3.000000:50:' | IFS='.:' read thd x mem; echo "'$thd' '$mem'";
'3' '50'
Or this:
$ sys='3.000000:50:'; IFS='.:' read thd x mem <<< "$sys"; echo "'$thd' '$mem'"
'3' '50'
The above sets the "dont care" variable x. If you do not like that, you can assign mem twice.
x
mem
$ sys='3.000000:50:'; IFS='.:' read thd mem mem <<< "$sys"; echo "'$thd' '$mem'"
'3' '50'
To read the file
sys something like this $ IFS='.:' read thd x mem; echo "'$thd' '$mem'"; < sys Which I found more difficult with multiple fields to read.– GeorgeC
Aug 29 at 20:37
sys
$ IFS='.:' read thd x mem; echo "'$thd' '$mem'"; < sys
The advantage of
read is, that it does not require two sub shells and two cut calls.– ceving
Aug 30 at 7:16
read
cut
I have played around with this one ' IFS='.:' read thd x mem x img x cal; echo "'$thd' '$mem' '$img' '$cal' "; < sys' how does the don't care variable work?
– GeorgeC
Aug 30 at 8:58
Should be
IFS='.:' read thd x mem x img x cal; echo "'$thd' '$mem' '$img' '$cal' "; < sys how does the don't care variable work?– GeorgeC
Aug 30 at 9:14
IFS='.:' read thd x mem x img x cal; echo "'$thd' '$mem' '$img' '$cal' "; < sys
When you split with
IFS='.:', you get three tokens: 3, 000000 and 50. Each token gets stored in one variable: thd=3, x=000000 and mem=50. You have to store the zeros somewhere, although you do not need them. You can also do unset x after the read. Or you can assign mem twice. First with the zeros and then with the 50.– ceving
Aug 30 at 9:30
IFS='.:'
thd=3
x=000000
mem=50
unset x
read
mem
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kindly include the input and complete desired output
– Inder
Aug 28 at 9:12