Get specific line from text file using just shell script

Question

I am trying to get a specific line from a text file   So far  online I have only seen stuff like sed   I can only use the sh -not bash or sed or anything like that   I need to do this only using a basic shell script   cat file   while read line     do         do something     done   I know how to iterate through lines  as shown above  but what if I just need to get the contents of a particular line

User · Answer

Assuming line is a variable which holds your required line number  if you can use head and tail  then it is quite simple   head -n  line file   tail -1   If not  this should work   x 0 want 5 cat lines   while read line  do   x     x 1      if    x -eq   want     then     echo  line     break   fi done

User · Answer

sed   sed  5 d  file   awk   awk  NR  5  file

User · Answer

line 5  prep  grep -ne   file txt   grep -e   line    echo    prep  line

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In parallel with William Pursell s answer  here is a simple construct which should work even in the original v7 Bourne shell  and thus also places where Bash is not available    i 0 while read line  do     i  expr   i    1      case  i in 5  echo   line   break   esac done  lt file   Notice also the optimization to break out of the loop when we have obtained the line we were looking for

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Best performance method  sed  5q d  file   Because sed stops reading any lines after the 5th one  Update experiment from Mr  Roger Dueck     I installed wcanadian-insane  6 6MB  and compared sed -n 1p  usr share dict words and sed  1q d   usr share dict words using the time command  the first took 0 043s  the second only 0 002s  so using  q  is definitely a performance improvement

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Easy with perl  If you want to get line 1  3 and 5 from a file  say  etc passwd   perl -e  while  lt  gt   if    l   1 3 5   print     lt   etc passwd

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If for example you want to get the lines 10 to 20 of a file you can use each of these two methods   head -n 20 york txt   tail -11   or   sed -n  10 20p  york txt    p in above command stands for printing   Here s what you ll see

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You could use sed -n 5p file   You can also get a range  e g   sed -n 5 10p file

User · Answer

The standard way to do this sort of thing is to use external tools   Disallowing the use of external tools while writing a shell script is absurd   However  if you really don t want to use external tools  you can print line 5 with   i 0  while read line  do test      i     5  amp  amp  echo   line   done  lt  input-file   Note that this will print logical line 5   That is  if input-file contains line continuations  they will be counted as a single line   You can change this behavior by adding -r to the read command   Which is probably the desired behavior

User · Answer

I didn t particularly like any of the answers   Here is how I did it     Convert the file into an array of strings lines   cat  foo txt       Print out the lines via array index echo    lines 0    echo    lines 1    echo    lines 5

[linux] Get specific line from text file using just shell script

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