我想撰寫一個 Bash 腳本，如果最后一列中的數字是奇數或偶數，或者如果文本檔案中的行中沒有數字，則可以列印，資料在 db.txt 檔案中看起來像這樣：
sdn sddjk@gmail 123
ksd 234
sddd sddsd@gmail
我試過這個：
#!/bin/bash
input="db.txt"
while IFS=" " read -r rec_column3
do
if [ $((number % 2)) -eq 0 ]; then
echo even
elif [ $((number % 2)) -eq 1 ]; then
echo odd
elif [[ "$rec_column3" != "number" ]]; then
echo not number
else
echo not found
fi
done
輸出是：
even
even
那么任何人都可以幫助我嗎？tnx
uj5u.com熱心網友回復：
#!/bin/bash
input="db.txt"
#########################
# check third field
#########################
echo "check third field"
while read -r _ _ rec_column3
do
if [[ -z "$rec_column3" ]]; then
echo "not found" >&2;
elif ! [[ $rec_column3 =~ ^[0-9] $ ]] ; then
echo "'$rec_column3' is not a number" >&2;
elif [[ $((rec_column3 % 2)) -eq 0 ]]; then
echo "'$rec_column3' is even" >&2
else
echo "'$rec_column3' is odd" >&2
fi
done < $input
echo "-----------------------"
#########################
# or check last field
#########################
echo "check last field"
while IFS=' ' read -r -a array
do
last_column=""
[[ ${#array[@]} -ne 0 ]] && last_column=${array[-1]}
if [[ -z "$last_column" ]]; then
echo "not found" >&2
elif ! [[ $last_column =~ ^[0-9] $ ]] ; then
echo "'$last_column' is not a number" >&2
elif [[ $((last_column % 2)) -eq 0 ]]; then
echo "'$last_column' is even" >&2
else
echo "'$last_column' is odd" >&2
fi
done < $input
$ cat db.txt
sdn sddjk@gmail 123
ksd 234
ksd
12345
sddd sddsd@gmail 234
sddd sddsd@gmail 111
sddd sddsd@gmail aaa
$ ./script.sh
check third field
'123' is odd
not found
not found
not found
not found
'234' is even
'111' is odd
'aaa' is not a number
-----------------------
check last field
'123' is odd
'234' is even
'ksd' is not a number
'12345' is odd
not found
'234' is even
'111' is odd
'aaa' is not a number
uj5u.com熱心網友回復：
awk可能是這項作業的更好工具。你可以做這樣的事情
awk 'BEGIN {split("even odd", a)} $NF ~ /^[0-9] $/ {print a[$NF%2 1]; next} {print "NAN"}' db.txt
檢查最后一個欄位是奇數還是偶數（ 1 是因為陣列a是從 1 開始的）。
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