如果行比x字符長，並添加字符串

Question

我都是新來的bash，我試圖解決一個問題。 我知道已經有類似問題的答案，但答案太複雜了。

我有一個變量與多行，我需要削減每行超過40個字符，並在其後添加「...：」。

但如果線路短於40個字符，我需要使它長40個字符，只添加「：」

所以它看起來像這樣：

var=this line is longer than 40 characters so it needs to be cut 
but this line is shorter 

，我需要它來尋找像這樣：

echo "$var" 
this line is longer than 40 characters s...: 
but this line is shorter     : 

在我的實際變量是10號線整體

Answer 1

可以在awk使用printf：

awk 'length > 40{$0 = substr($0, 1, 40) "..."} {printf "%-43s:\n", $0}' <<< "$var" 

this line is longer than 40 characters s...: 
but this line is shorter     : 

或使其接受來自命令行參數：

awk -v n=40 -v r='...' 'length > n{$0 = substr($0, 1, n) r} 
{printf "%-" n + length(r) "s:\n", $0}' <<< "$var" 

this line is longer than 40 characters s...: 
but this line is shorter     : 

Answer 2

AWK方法：

echo $var | awk '{printf("%-40s"((length($0)>40)?"...":" ")":\n", substr($0,1,40))}' 

輸出：

this line is longer than 40 characters s...: 
but this line is shorter     : 

Answer 3

或者我們可以留在bash：

var='this line is longer than 40 characters so it needs to be cut 
but this line is shorter' 

while IFS=$'\n' read -r line 
do 
    if ((${#line} > 36)) 
    then 
     line="${line:0:36}...:" 
    else 
     ((diff = 40 - ${#line})) 
     printf -v line "%s%${diff}s\n" "$line" "...:" 
    fi 

    echo "$line" 
done<<<"$var" 

如awk顯然其它命令可以做短:)

也不清楚，如果整條生產線是爲40個字符或40該行加上額外的'...：'。容易改變:)