奇怪的sed

qzhu

Haven't done much scripting lately.

OS: tru64unix V4.0G, Shell: csh
# which sed
/usr/bin/sed
# echo "a b" | sed 's/ /\t/'
atb
# echo "a b" | sed 's/ /\\\t/'
a\tb

???
I am expecting a TAB between "a" and "b", not "atb" nor "a\tb", what am I doing wrong?
Seems sed won't recognize all escape sequences such as \n,\t,\r,\b ...
Anyone has comment on this? much appreciated.

lightspeed

與 不同系統(tǒng)及版本的 sed 有關.  一般 sed 很可能只有 \  \n  &  三個特殊字符. 如果是這樣,用 " 代替 '

# echo "a b"|sed "s/ /\t/"

zhiguo_luan

好像還是不行，偶的是GNU３．０２

lightspeed

GNU 3.02 不支持 \t,  3.02.80 以上可以。

再試一次：

echo "a b"|sed "s/ /`echo \\\t`/"

不行的話， 就升級吧。

zhiguo_luan

OK

qzhu

看樣子在某些版本中如果\t不管用，直接輸入TAB就可以了。

http://www.unixguide.net/unix/sedoneliner.shtml

USE OF '\t' IN SED SCRIPTS: For clarity in documentation, we have used the expression '\t' to indicate a tab character (0x09) in the scripts. However, most versions of sed do not recognize the '\t' abbreviation, so when typing these scripts from the command line, you should press the TAB key instead. '\t' is supported as a regular expression metacharacter in awk, perl, and in a few implementations of sed.