[SOLVED] Syntax Grep and Cat

ifeatu · 04-22-2010, 05:35 PM

I'm trying to give a single user a membership to multiple Unix groups...my syntax appears to work to stdout but I can't get it to append to the file itself:

Code:

grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' > group.tmp

This command overwrites the group.tmp file with nothingness. How would I incorporate cat? So far I tried

Code:

(grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' | cat > group.tmp

and

Code:

grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' | cat

tuxdev · 04-22-2010, 05:55 PM

You can't read and write to the same file in the same pipeline. Use a temp.

Sergei Steshenko · 04-22-2010, 05:58 PM

Quote:

Originally Posted by ifeatu

I'm trying to give a single user a membership to multiple Unix groups...my syntax appears to work to stdout but I can't get it to append to the file itself:

Code:

grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' > group.tmp

This command overwrites the group.tmp file with nothingness. How would I incorporate cat? So far I tried

Code:

(grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' | cat > group.tmp

and

Code:

grep printeradmin group.tmp | sed 's/$/',abrambila,root,administrator,Administrator,alekich,alice,andra,backuppc,bogus1,colofson,Contreras,dave,domainer,don,dthompson,dthompson_new,elaine,fseto,groberts,inf09$,inf11,inmantmp,jeff,jlasky,joel,jwenceslao,katy,klance,lfrantz,lhills,lhoward,madelyn,mcarter,root,nbaldwin,pmalbrough,printeradmin,rmok,rreyes,savin,savin$,sfriese,stevenc,stevenf,stvn,tftpd,tsmith,ttorbon,root,vheistermann,wbaatin,wmadden'/' | cat

Do you need the items in red ? I mean in the first code snippet.

Sergei Steshenko · 04-22-2010, 06:00 PM

Quote:

Originally Posted by tuxdev

You can't read and write to the same file in the same pipeline. Use a temp.

Yep.

grail · 04-22-2010, 08:38 PM

I would be asking why bother with the grep at all seeing sed can just as easily find "printeradmin"??

Code:

sed -i '/<what you are looking for>/s/<what you want to change>/<changes you want/' file

grail · 05-16-2010, 12:17 AM

Please mark as SOLVED if you have no more questions