如何连接每条双线?

paste -s -d ':\n' file 应该这么做。

例如:

% cat f
a1
a2
b1
b2
% paste -s -d ':\n' f
a1:a2
b1:b2

sed 'N;s/\n/:/;' < srcfile > destfile

看 over there 我发现了一个可以转换为:

sed '$!N;s/\n/:/' < file

INDEX=0
A=""
B=""

for i in `awk '{print $1}' input`
    do
    if [ $INDEX -eq 0 ]; then
        A=$i;
        let INDEX=1;
    fi

    if [ $INDEX -eq 1 ]; then
        B=$i;
        echo $A:$B
        let INDEX=0;
    fi
done

awk '{line=$0; printf line; if (getline) printf ":" $0; print ""}' inputfile

使用备份就地编辑:

perl -i.bak -pe 's/\n\Z/:/ if $.%2' file

就地编辑无备份:

perl -i -pe 's/\n\Z/:/ if $.%2' file

以下是python中的一个解决方案:

#!/usr/bin/python3

def njoin(filename, outfn="", n=3, linesuffix=" "):
    if not outfn:
        outfn = filename + ".join"
    with open(filename) as infh, open(outfn, "w") as outfh:
        nline = 0
        for line in infh:
            if nline % n != n-1:
                line = line.rstrip() + linesuffix
            outfh.write(line)
            nline += 1

在这种情况下,可以使用如下函数:

njoin("/path/to/file", n=2, linesuffixe=":")