title: error when edditing big text file using awk
body: <p>I have a text file like the following small example:</p>
  
  <pre><code>chr1    HAVANA  transcript  12010   13670   .   +   .   gene_id "ENSG00000223972.4"; transcript_id "ENST00000450305.2"; gene_type "pseudogene"; gene_status "KNOWN"; gene_name "DDX11L1"; tr
  anscript_type "transcribed_unprocessed_pseudogene"; transcript_status "KNOWN"; transcript_name "DDX11L1-001"; level 2; ont "PGO:0000005"; ont "PGO:0000019"; havana_gene "OTTHUMG00000000961.2"; havana_tran
  script "OTTHUMT00000002844.2";
  chr2    HAVANA  exon    12010   12057   .   +   .   gene_id "ENSG00000223972.4"; transcript_id "ENST00000450305.2"; gene_type "pseudogene"; gene_status "KNOWN"; gene_name "DDX11L1"; transcript
  _type "transcribed_unprocessed_pseudogene"; transcript_status "KNOWN"; transcript_name "DDX11L1-001"; exon_number 1; exon_id "ENSE00001948541.1"; level 2; ont "PGO:0000005"; ont "PGO:0000019"; havana_gene
   "OTTHUMG00000000961.2"; havana_transcript "OTTHUMT00000002844.2";
  chr3    HAVANA  exon    12179   12227   .   +   .   gene_id "ENSG00000223972.4"; transcript_id "ENST00000450305.2"; gene_type "pseudogene"; gene_status "KNOWN"; gene_name "DDX11L1"; transcript
  _type "transcribed_unprocessed_pseudogene"; transcript_status "KNOWN"; transcript_name "DDX11L1-001"; exon_number 2; exon_id "ENSE00001671638.2"; level 2; ont "PGO:0000005"; ont "PGO:0000019"; havana_gene
   "OTTHUMG00000000961.2"; havana_transcript "OTTHUMT00000002844.2";
  </code></pre>
  
  <p>in the file there are different lines. each line starts with <code>chr</code>. every line has some columns and separators are either tab or ";". 
  I want to make a new file from this one in which there would be a change only in columns 4 and 5. in fact column 4 in the new file would be <code>((column 4 in original file)-12)</code> and 5th column in the new file would be <code>((column 4 in original file)+50)</code>. I tried to do that in <code>awk</code> using the following command:</p>
  
  <pre><code>awk 'BEGIN { FS="\t;" } {print  $1"\t"$2"\t"$3"\t"$4=$4-12"\t"$5=$4+50"\t"$6"\t"$7"\t"$8"\t"$9" "$10";"$11" "$12";"$13" "$14";"$15" "$16";"$17" "$18";"$19" "$20";"$21" "$22";"$23" "$24";"$25" "$26";"$27" "$28";"$29" "$30";"$31" "$32";"$33" "$34";"$35" "$36";"$37" "$38";" }' input.txt &gt; test2.txt
  </code></pre>
  
  <p>when I run the code, it would return this error:</p>
  
  <pre><code>awk: cmd. line:1: BEGIN { FS="\t;" } {print  $1"\t"$2"\t"$3"\t"$4=$4-12"\t"$5=$4+50"\t"$6"\t"$7"\t"$8"\t"$9" "$10";"$11" "$12";"$13" "$14";"$15" "$16";"$17" "$18";"$19" "$20";"$21" "$22";"$23" "$24";"$25" "$26";"$27" "$28";"$29" "$30";"$31" "$32 ";" $33" "$34";"$35" "$36";"$37" "$38";" }
  awk: cmd. line:1:                                                                                                                                                                                                                         ^ syntax error
  awk: cmd. line:1: BEGIN { FS="\t;" } {print  $1"\t"$2"\t"$3"\t"$4=$4-12"\t"$5=$4+50"\t"$6"\t"$7"\t"$8"\t"$9" "$10";"$11" "$12";"$13" "$14";"$15" "$16";"$17" "$18";"$19" "$20";"$21" "$22";"$23" "$24";"$25" "$26";"$27" "$28";"$29" "$30";"$31" "$32 ";" $33" "$34";"$35" "$36";"$37" "$38";" }
  awk: cmd. line:1:                                                                                                                                                                                                                                      ^ syntax error
  </code></pre>
  
  <p>do you know how to fix it?</p>