Conditional statements

[Adrian Manolache]

What i want to do: list all users that have UID > 2000.
I know i can find information regarding the user in /etc/passwd and i know how to select only the fields i'm interested in from that file using (cut -f1,3 -d . But what composed command will solve my problem? How to i check if the 3'rd field returned by cat is greater that 2000 ?

[i92guboj]

You can use awk for the whole task:

awk '{FS=":"; if ($3 > 2000) print $1":"$3}' /etc/passwd

[Adrian Manolache]

Thanks, that worked! I'm curious though: are there any approaches that don't use awk?

[i92guboj]

Thanks, that worked! I'm curious though: are there any approaches that don't use awk?

Sure, this is a bashish approach:

#!/bin/bash

cat /etc/passwd | while read line
do
a=${line%%:*}
b=${line%:*:*:*:*}
b=${b#*:*:}

if [ "$b" -gt "2000" ]
then
echo $a:$b
fi
done

[Cabhan]

I prefer to use cut:

#!/bin/bash

exec 3< /etc/passwd

while read line <&3; do
    name=$(echo "$line" | cut -f1 -d:)
    id=$(echo "$line" | cut -f3 -d:)

    if [ "$id" -gt 2000 ]; then
        echo "$name"
    fi
done

awk is incredibly powerful (and may well be better suited to this problem), but cut is a less powerful alternative in many cases.

[ghostdog74]

awk '{FS=":"; if ($3 > 2000) print $1":"$3}' /etc/passwd

it is advisable to put FS declaration in the BEGIN block or using -F option

awk 'BEGIN{FS=":"} $3 > 2000 {print ...}' /etc/passwd

[ghostdog74]

Thanks, that worked! I'm curious though: are there any approaches that don't use awk?

bash, no cat

while IFS=":" read -r -a line
do
 if [ ${line[2]} -gt 2000 ];then
   echo ${line[0]} ${line[2]}
 fi
done < /etc/passwd