CIS 218 stream editor (sed) CIS 218 Advanced UNIX 1 sed Uses - PowerPoint PPT Presentation

CIS 218 stream editor (sed) CIS 218 Advanced UNIX 1

sed • Uses same syntax as vi • Batch front end to same ed command • Works record by record thru entire file • sed [-n] script [filelist] or sed [-n] -f scriptfile [filelist] • • if no filelist is given, it is often used in a pipe • script = one or more lines in the following format: [address[,address]] instruction [argument list] CIS 218 Advanced UNIX 2

sed • Addressing can be the same as we saw in vi, but it can also be regular expressions to match instructions can be any one from the list: • d - delete • n - next • a - append • i - insert • c - change • s - substitute • p - print • w - write • r - read • q – quit • to modify the instructions you can also use – ! - not - to mean if it does not match – { } - to group the instructions together on a single match • the -n says don't print a line to the output unless specifically instructed to. Default is to print all lines. • s (substitute) is the same command specified in vi and regular expressions: s/old/new/[g] CIS 218 Advanced UNIX 3

sed Examples % sed '3,6 p' file - print all lines, duplicates lines 3, 4, 5, • and 6 in the output % sed -n '3,6 p' file - will print only the lines 3 thru 6 • to the output • % sed -n '/line/ p' file - will print any lines that contain the string "line“ • sed commands often put into a sed-script file: cat pscript 3,6 p • sed -n -f pscript file will print the lines 3thru 6 to output • or used in a pipe: who | sed -n -f pscript | more CIS 218 Advanced UNIX 4

Sed remembering what was found • Things enclosed in the \( \) pair will be stored (up to 9) to be used as \1 , \2 ... \9 % cat rev.script • s/^\([0-9]\)\([0-9]\)/\2and\1/ • % cat num.file 23 Jan 43 Pete 72 Fred 91 Mike • % sed -f rev.script numfile 32 Jan 34 Pete 27 Fred 19 Mike CIS 218 Advanced UNIX 5