Use sed to change an entry of a configuration file -

-

i want change following line in /etc/security/limits.conf from

#*               soft    core           0

to 

*               soft    core            unlimited

to enable core dump.

i tried use following sed command did nothing:

sed -e "s/^\#\*\([ ]+soft[ ]+core\)[0-9][0-9]*$/\*\1 unlimited/" limits.conf

where did wrong?

mechanics of sed

there variety of issues:

  1. you don't need backslash in front of #, nor in front of * in replacement text. don't harm, not necessary.
  2. you need allow spaces between core , number.
  3. you didn't allow blanks , tabs in file.
  4. you didn't allow trailing white space on line (which might not matter).
  5. you didn't explicitly enable extended regular expressions, , did use old-style \(…\) capturing notation, means + has no special meaning.
  6. you didn't modify file in place -i option (which fine while you're getting sed command correct).

you should able use (gnu sed):

sed -r -e "s/^#\*([[:space:]]+soft[[:space:]]+core)[[:space:]]+[0-9][0-9]*[[:space:]]*$/\*\1 unlimited/" limits.conf

the [[:space:]] notation recognizes sorts of white space (including newlines, etc); use [[:blank:]] recognizes blanks , tabs if prefer.

you use old-style notation:

sed -e "s/^#\*\([[:space:]]\{1,\}soft[[:space:]]\{1,\}core\)[[:space:]]\{1,\}[0-9][0-9]*[[:space:]]*$/*\1 unlimited/" limits.conf

if want preserve white space between core , number, can:

sed -e "s/^#\*\([[:space:]]\{1,\}soft[[:space:]]\{1,\}core[[:space:]]\{1,\}\)[0-9][0-9]*[[:space:]]*$/*\1unlimited/" limits.conf

the close capture moved, , there's no need add space in replacement string.

be cautious when modifying system file

note should careful when sure script ready modify production file. create new file, check it, copy old file date/time-stamped file name, , copy new file on original. alternatively, use suffix -i, date/time again.

sed -i .$(date +'%y%m%d.%h%m%s') -e "s/^#\*\([[:space:]]\{1,\}soft[[:space:]]\{1,\}core[[:space:]]\{1,\}\)[0-9][0-9]*[[:space:]]*$/*\1unlimited/" limits.conf

the advantage of format (which based on iso 8601:2004) successive files sort date order without special sorting options. can add punctuation date/time format if wish.

either way, if new file gives problems, you've got (a copy of) original can put system running again smoothly reasonably feasible.


Comments

Post a Comment

Popular posts from this blog

node.js - Mongoose: Cast to ObjectId failed for value on newly created object after setting the value -

-
this question has answer here: what's mongoose error cast objectid failed value xxx @ path “_id”? 7 answers even though has been asked many times because entity has no valid objectid field. i came across situation objectid set value can casted objectid still error. the schema: var serviceschema = parammongoose.schema({ servicename:{ type: parammongoose.schema.types.objectid , ref: 'servicenames',required:true } }); pseudo code: servicefromdb=new service({servicename:'some name'}); servicefromdb.servicename='000000000000000000000001'; servicefromdb.save(function(paramerror,paramdata){ if(paramerror){ console.log('but but...',servicefromdb,paramerror) } }); the output of code is: but but... { servicename: 000000000000000000000001, _id: 55079a90286f49280364f78b } { [casterror: cast objectid faile...
Read more

gradle error "Cannot convert the provided notation to a File or URI" -

-
i have defined 2 system properties in gradle.properties: systemprop.builddir=build systemprop.cfgdir=build\\cfg and have following task defined in build.gradle: task clean(group:'clean',description:'clean project') << { ant.sequential { delete(dir: system.properties.builddir) mkdir(dir: system.properties.builddir) delete(dir: system.properties.cfgdir) mkdir(dir: system.properties.cfgdir) } } this generates following error: execution failed task ':clean'. > cannot convert provided notation file or uri: {dir=build}. following types/formats supported: - string or charsequence path, e.g 'src/main/java' or '/usr/include' - string or charsequence uri, e.g 'file:/usr/include' - file instance. - uri or url instance. but equivalent block of code not generate error , works expected: task clean(group:'clean',description:'clean project') << { ...
Read more

ios - Possible to get UIButton sizeThatFits to work? -

-
i have been using method of resizing uibuttons depreciated, , not robust. , other reasons, want sizethatfits work uibuttons. i've read online, i'm not sure if should work (seems working some, not others, difference maybe between style, i'm using custom). here simple test code recreate issue (i put in viewdidload test, shouldn't matter, , real code part of large project): uibutton *btn = [uibutton buttonwithtype:uibuttontypecustom]; [btn settitle:@"this test long title need word wrap more single line when displayed on tiny ipod in portrait view." forstate:uicontrolstatenormal]; btn.titlelabel.linebreakmode = uilinebreakmodewordwrap; // depreciated - nothing replace it? cgrect r = btn.frame; r.origin.x = 0; r.origin.y = 0; r.size.width = 320; r.size.height = [btn.titlelabel.text sizewithfont:btn.titlelabel.font constrainedtosize:cgsizemake(r.size.width,100000) linebreakmode:btn.titlelabel.linebreakmode].height; // returns approx 86 , changes correctly ...
Read more