awk 'BEGIN{fs=10.0;for (i = 0; i < 10000; i++){t=i/fs; print t, sin(2*3.14*t*10)}}' > hoge.txt

# もっと桁数が欲しい場合は
# ちなみに後述のawkコマンドを走らせてきちんと結果を得るためには桁数が必要なので、こっちで
awk 'BEGIN{fs=10.0;for (i = 0; i < 10000; i++){t=i/fs; printf "%.10e %.10e\n", t, sin(2*3.14*t*10)}}' > hoge.txt

awk 'NR==1 {max=$1} {if($1 > max) max = $1} END {print max}' hoge.txt

awk 'NR==1 {min=$1} {if($1 < min) min = $1} END {print min}' hoge.txt

awk 'NR==1{x=0} NR>1 {diff1=diff2; diff2=$2-x; x=$2} {if(diff1*diff2<0)print $1}' hoge.txt > foo.txt

plot "hoge.txt" w l lw 2 lc 6, "foo.txt" w p pt 5 ps 2 lc 7

awk 'NR==1{x=0} NR>1 {diff1=diff2; diff2=$2-x; x=$2} {if(diff1*diff2<0 && diff1>0)print $1, 1}' hoge.txt > maximum.txt
awk 'NR==1{x=0} NR>1 {diff1=diff2; diff2=$2-x; x=$2} {if(diff1*diff2<0 && diff1 <0) print $1,-1 }' hoge.txt > minimum.txt

plot "hoge.txt" w l lw 2 lc 6, "maximum.txt" w p pt 5 ps 2 lc 7, "minimum.txt" w p pt 5 ps 2 lc 4