# align all text flush right on a 79-column width #右对齐，按79列宽排列所有文本 sed -e :a -e 's/^.\{1,78\}$/ &/;ta' # set at 78 plus 1 space
t命令的manIf a s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script.一个s///命令成功替换后，那就流程就分支到label出，没成功替换就分支到脚本底部。
-e选项 add the script to the commands to be executed
整体语句的逻辑就是循环把有78个字符替换成空格加它们本身(也就是79列)。
# center all text in the middle of 79-column width. In method 1, # spaces at the beginning of the line are significant, and trailing # spaces are appended at the end of the line. In method 2, spaces at # the beginning of the line are discarded in centering the line, and # no trailing spaces appear at the end of lines. #使所有文本居于79列宽的格式中央。在第一种方法中，每一行开头处的空格是 #很重要的，最后的空格被附在行尾。第二种方法中，一行开头的空格在中心对 #齐的行中被丢弃，行尾也没有原来结尾处的空格。 sed -e :a -e 's/^.\{1,77\}$/ & /;ta' # method 1 sed -e :a -e 's/^.\{1,77\}$/ &/;ta' -e 's/\(*\)1/\1/' # method 2
这个语句和上面的类似，不再赘述。
