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Comment: Agree with Lhunath - rm useless note. Fix writing style.
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Comment: note about the head|tail approach
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| {{{ sed -n ${n}p "$file" |
{{{#!highlight bash sed -n "${n}p" "$file" |
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| But this reads the entire file even if only the third line is desired, which can be avoided by printing line {{{$n}}} using the "p" command, followed by a "q" to exit the script: | |
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| {{{ sed -n "$n{p;q;}" "$file" |
But this reads the entire file even if only the third line is desired, which can be avoided by using the `q` command to quit on line `$n`, and deleting all other lines with the `d` command: {{{#!highlight bash sed "${n}q;d" "$file" |
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| Another method is to grab the last line from a listing of the first {{{n}}} lines: | |
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| {{{ head -n $n $file | tail -n 1 |
Another method is to grab the last line from a listing of the first `n` lines. However, this is only applicable if you know the file has at least `n` lines. {{{#!highlight bash head -n "$n" "$file" | tail -n 1 |
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| {{{ awk "NR==$n{print;exit}" file |
{{{#!highlight bash awk "NR==$n{print;exit}" "$file" |
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| {{{ x=3 y=4 sed -n "$x,${y}p;${y}q;" "$file" # Print lines $x to $y; quit after $y. head -n $y "$file" | tail -n $((y - x + 1)) # Same head -n $y "$file" | tail -n +$x # If your tail supports it awk "NR>=$x{print} NR==$y{exit}" "$file" # Same |
{{{#!highlight bash x=3 y=4 sed -n "$x,${y}p;${y}q;" "$file" # Print lines $x to $y; quit after $y. head -n "$y" "$file" | tail -n "$((y - x + 1))" # Same head -n "$y" "$file" | tail -n "+$x" # If your tail supports it awk "NR>=$x{print} NR==$y{exit}" "$file" # Same |
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| In Bash 4, a pure-bash solution can be achieved succinctly using the {{{mapfile}}} builtin. More than one line can be read into the array {{{MAPFILE}}} by adjusting the argument to mapfile's -n option: | |
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| {{{ mapfile -ts $((n-1)) -n 1 < "$file" echo "${MAPFILE[0]}" |
Or a counter with a simple `read` loop: {{{#!highlight bash # Bash/ksh m=0 while ((m++ < n)) && read -r _; do : done head -n 1 |
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| {{{mapfile}}} can also be used similarly to {{{head}}} while avoiding buffering issues in the event input is a pipe: | |
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| {{{ { mapfile -n $n; head -n 1; } <"$file" |
To read into a variable, it is preferable to use `read` or `mapfile` rather than an external utility. More than one line can be read into the given array variable or the default array `MAPFILE` by adjusting the argument to mapfile's -n option: {{{#!highlight bash # Bash4 mapfile -ts "$((n - 1))" -n 1 x <"$file" printf '%s\n' "$x" |
How can I print the n'th line of a file?
One dirty (but not quick) way is:
1 sed -n "${n}p" "$file"
But this reads the entire file even if only the third line is desired, which can be avoided by using the q command to quit on line $n, and deleting all other lines with the d command:
1 sed "${n}q;d" "$file"
Another method is to grab the last line from a listing of the first n lines. However, this is only applicable if you know the file has at least n lines.
1 head -n "$n" "$file" | tail -n 1
Another approach, using AWK:
1 awk "NR==$n{print;exit}" "$file"
If more than one line is needed, it's easy to adapt any of the previous methods:
Or a counter with a simple read loop:
To read into a variable, it is preferable to use read or mapfile rather than an external utility. More than one line can be read into the given array variable or the default array MAPFILE by adjusting the argument to mapfile's -n option: