SED (Stream EDitor)

SED

Find and Replace:

Sed is often used as a find-and-replace tool.

     sed 's/Glenn/Harold/g' oldfile >newfile

will replace every occurrence of "Glenn" with the word "Harold", wherever it occurs in the file. The "find" portion is a regular expression ("RE"), which can be a simple word or may contain special characters to allow greater flexibility (for example, to prevent "Glenn" from also matching "Glennon").

SED Leaving Space:

My very first use of sed was to add 8 spaces to the left side of a file, so when I printed it, the printing wouldn't begin at the absolute left edge of a piece of paper.

     sed 's/^/        /' myfile >newfile   # my first sed script
    sed 's/^/        /' myfile | lp       # my next sed  script

SED display one paragraph of a file:

sed could display only one paragraph of a file, beginning at the phrase "and where it came" and ending at the phrase "for all people". My script looked like this:

     sed -n '/and where it came/,/for all people/p' myfile

SED Display 12 to 18 lines:

found that sed could show me only (say) lines 12-18 of a file and not show me the rest. This was very handy when I needed to review only part of a long file and I didn't want to alter it.

     # the 'p' stands for print
   sed -n 12,18p myfile

SED Display everything but of those 12, 18:

sed could show me everything else BUT those particular lines, without physically changing the file on the disk:

     # the 'd' stands for delete
   sed 12,18d myfile

SED double-space my single-spaced file when it came time to print it:

double-space my single-spaced file when it came time to print it:

     sed G myfile >newfile