Cut command, order not preserved

cut

I have a sample file:-

[root@localhost base_filters]# cat shortlist
2233|charles harris  |g.m.     |sales     |12/12/52| 90000
9876|bill johnson    |director |production|03/12/50|130000
5678|robert dylan    |d.g.m.   |marketing |04/19/43| 85000
2365|john woodcock   |director |personnel |05/11/47|120000
5423|barry wood      |chairman |admin     |08/30/56|160000

I wanted to flip the names in the file such that there is a comma , after the last name i.e for example a name should appear as harris,charles.

I tried the following command:-

[root@localhost base_filters]# tr -s ' ' < shortlist | cut -d\| -f2 | cut -d' ' -f2,1
charles harris
bill johnson
robert dylan
john woodcock
barry wood

I want last name to appear first so I specified field 2 and then 1 but this doesn't seem to work. Any Ideas about this?

Best Answer

This is done easily using awk. First print out the name, then pipe the output to awk again (this time using space as the file separator).

awk -F "|" '{print $2}' extract.txt | awk -F " " '{print $2 "," $1}'

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Not getting desired output with cut command

With -d " ", the field separator is one (and only one) space character. Contrary to the shell word splitting, cut doesn't treat space any different than any other character. So cut -d " " -f2 returns "" in root 19, just like it would return "" for cut -d: -f2 in root:::19.

You'd need to either squeeze the blanks to transform any sequence of space into one space:

ps aux | grep ata | tr -s ' ' | cut -d ' ' -f2

Or use awk where in its default spitting mode, it doesn't use a separator but splits into the list of sequences of non-blank characters:

ps aux | awk '/ata/{print $2}'

In this case though, you may want to use:

pgrep -f ata

Or at least:

ps -eo pid= -o args= | awk '/ata/{print $1}'

To match against the arguments only.

Cut command fields

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

Best Answer

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