User:Timothee Flutre/Notebook/Postdoc/2012/05/25

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==Entry title==
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==One-liners with GNU tools==
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* Insert content here...
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* '''Toolbox''': often available by default on many computers running GNU/Linux
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** [https://en.wikipedia.org/wiki/Bash_%28Unix_shell%29 Bash]
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** [https://en.wikipedia.org/wiki/AWK AWK]
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** [https://en.wikipedia.org/wiki/Grep grep]
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** [https://en.wikipedia.org/wiki/Sed sed]
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** [https://en.wikipedia.org/wiki/GNU_Core_Utilities GNU coreutils] (head, tail, cut, uniq, sort, tr, ...)
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* '''Tutorials''':
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** [http://en.flossmanuals.net/command-line/index/ Introduction to the command-line]
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** [http://www.ibm.com/developerworks/aix/library/au-unixtext/index.html Introduction to text manipulation on UNIX-based systems] by Brad Yoes (IBM)
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* '''Skip a subset of successive lines''':
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for i in {1..10}; do echo $i; done | sed 3,6d
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* '''Extract a subset of successive lines''':
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$ for i in {1..20}; do echo $i; done | sed -n 3,5p
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* '''Use absolute values:'''
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$ for i in {-5..5}; do echo $i; done | awk 'function abs(x){return (((x < 0.0) ? -x : x) + 0.0)} {print abs($1)}'
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* '''Extract the best snp per gene''':
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$ echo -e "gene\tsnp\tpvalue\ng1\ts1\t0.3\ng1\ts2\t0.002\ng2\ts2\t0.7\ng2\ts3\t0.05" > dat.txt
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gene    snp    pvalue
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g1      s1      0.3
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g1      s2      0.002
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g2      s2      0.7
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g2      s3      0.05
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$ cat dat.txt | sed 1d | sort -k1,1 -k3,3 | awk '{print $3"\t"$2"\t"$1}' | uniq -f2
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g1      s2      0.002
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g2      s3      0.05
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* '''Loop over pairs''':
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$ subgroups=("s1" "s2" "s3" "s4"); for i in {0..2}; do let a=$i+1; for j in $(seq $a 3); do s1=${subgroups[$i]}; s2=${subgroups[$j]}; echo $s1 $s2; done; done
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* '''Convert file from fasta to fastq''': we can use the built-in variable "RS" ([http://www.gnu.org/software/gawk/manual/gawk.html#Records split records]) and use "split" ([http://www.gnu.org/software/gawk/manual/gawk.html#String-Functions string function]):
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<nowiki>
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$ awk 'BEGIN{RS=">"} {if(NF==0)next; split($0,a,"\n"); printf "@"a[1]"\n"a[2]"\n+\n"; \
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for(i=1;i<=length(a[2]);i++)printf "}"; printf"\n"}' probes.fa > probes.fq
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</nowiki>
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* '''Sort a file with header line''': that is, we don't want the first line to be sorted
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$ echo -e "x\ty"; for i in {1..10}; do echo -e $i"\t"$RANDOM; done | (read -r; printf "%s\n" "$REPLY"; sort -k2,2n)
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* '''Get rows from a big file which are also in a small file''': example of using awk with 2 input files by loading the important information from the small file into an array in memory, then parsing the big file line by line and comparing each with the content of the array
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$ echo -e "gene\tsnp\tpvalue\ngene1\tsnp1\t0.002\ngene2\tsnp2\t0.8\ngene2\tsnp3\t0.1" > file_all.txt
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$ echo -e "gene1\tsnp1" > file_subset.txt
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$ awk 'NR==FNR{a[$1$2]++;next;}{x=$1$2;if(x in a)print $0}' file_subset.txt <(sed 1d file_all.txt)

Revision as of 01:00, 4 November 2013

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One-liners with GNU tools

  • Toolbox: often available by default on many computers running GNU/Linux



  • Skip a subset of successive lines:
for i in {1..10}; do echo $i; done | sed 3,6d


  • Extract a subset of successive lines:
$ for i in {1..20}; do echo $i; done | sed -n 3,5p


  • Use absolute values:
$ for i in {-5..5}; do echo $i; done | awk 'function abs(x){return (((x < 0.0) ? -x : x) + 0.0)} {print abs($1)}'


  • Extract the best snp per gene:
$ echo -e "gene\tsnp\tpvalue\ng1\ts1\t0.3\ng1\ts2\t0.002\ng2\ts2\t0.7\ng2\ts3\t0.05" > dat.txt
gene    snp     pvalue
g1      s1      0.3
g1      s2      0.002
g2      s2      0.7
g2      s3      0.05
$ cat dat.txt | sed 1d | sort -k1,1 -k3,3 | awk '{print $3"\t"$2"\t"$1}' | uniq -f2
g1      s2      0.002
g2      s3      0.05


  • Loop over pairs:
$ subgroups=("s1" "s2" "s3" "s4"); for i in {0..2}; do let a=$i+1; for j in $(seq $a 3); do s1=${subgroups[$i]}; s2=${subgroups[$j]}; echo $s1 $s2; done; done


$ awk 'BEGIN{RS=">"} {if(NF==0)next; split($0,a,"\n"); printf "@"a[1]"\n"a[2]"\n+\n"; \
for(i=1;i<=length(a[2]);i++)printf "}"; printf"\n"}' probes.fa > probes.fq


  • Sort a file with header line: that is, we don't want the first line to be sorted
$ echo -e "x\ty"; for i in {1..10}; do echo -e $i"\t"$RANDOM; done | (read -r; printf "%s\n" "$REPLY"; sort -k2,2n)


  • Get rows from a big file which are also in a small file: example of using awk with 2 input files by loading the important information from the small file into an array in memory, then parsing the big file line by line and comparing each with the content of the array
$ echo -e "gene\tsnp\tpvalue\ngene1\tsnp1\t0.002\ngene2\tsnp2\t0.8\ngene2\tsnp3\t0.1" > file_all.txt
$ echo -e "gene1\tsnp1" > file_subset.txt
$ awk 'NR==FNR{a[$1$2]++;next;}{x=$1$2;if(x in a)print $0}' file_subset.txt <(sed 1d file_all.txt)



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