Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression

/
/
gms

Test String

Code Generator

Generated Code

const regex = /(?P<file_number>\d+)\.\s+(?P<filepath>.*?)\n(?P<file_contents>```(.*?)```)(?=\d+\.\s+|$)/gms; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?P<file_number>\\d+)\\.\\s+(?P<filepath>.*?)\\n(?P<file_contents>```(.*?)```)(?=\\d+\\.\\s+|$)', 'gms') const str = `1. nextflow.config \`\`\` params { inputDir = "data/raw" outputDir = "results" } process { executor = "local" memory = "8 GB" cpus = 4 } \`\`\` 2. main.nf \`\`\` #!/usr/bin/env nextflow params.inputDir = "./data/raw" params.outputDir = "./results" include { preprocess, qualityControl, differentialExpression } from "./scripts" workflow { input: path(inputDir) from params.inputDir output: path(outputDir) into results preprocess_output, quality_control_output, differential_expression_output = script { preprocess(inputDir) } quality_control_output = script { qualityControl(preprocess_output) } differential_expression_output = script { differentialExpression(preprocess_output) } } \`\`\` 3. scripts/preprocess.sh \`\`\` #!/bin/bash inputDir=\$1 # Trim reads using Trimmomatic trimmomatic PE \${inputDir}/sample_R1.fastq.gz \${inputDir}/sample_R2.fastq.gz \${inputDir}/sample_R1.trimmed.fastq.gz \${inputDir}/sample_R1.unpaired.fastq.gz \${inputDir}/sample_R2.trimmed.fastq.gz \${inputDir}/sample_R2.unpaired.fastq.gz ILLUMINACLIP:adapters.fa:2:30:10 LEADING:3 TRAILING:3 SLIDINGWINDOW:4:15 MINLEN:36 # Align trimmed reads using HISAT2 hisat2 -x genome_index -1 \${inputDir}/sample_R1.trimmed.fastq.gz -2 \${inputDir}/sample_R2.trimmed.fastq.gz -S \${inputDir}/sample.sam # Convert SAM to BAM samtools view -bS \${inputDir}/sample.sam > \${inputDir}/sample.bam # Sort BAM file samtools sort \${inputDir}/sample.bam -o \${inputDir}/sample.sorted.bam # Index sorted BAM file samtools index \${inputDir}/sample.sorted.bam # Remove intermediate files rm \${inputDir}/sample.sam \${inputDir}/sample.bam \`\`\` 4. scripts/quality_control.sh \`\`\` #!/bin/bash inputDir=\$1 # Run FastQC on trimmed reads fastqc \${inputDir}/sample_R1.trimmed.fastq.gz \${inputDir}/sample_R2.trimmed.fastq.gz -o \${inputDir} # Move FastQC output to results directory mv \${inputDir}/*.html \${inputDir}/*.zip \${inputDir}/../results/logs \`\`\` 5. scripts/differential_expression.sh \`\`\` #!/bin/bash inputDir=\$1 # Count reads using featureCounts featureCounts -T 4 -a annotation.gtf -o \${inputDir}/counts.txt \${inputDir}/sample.sorted.bam # Perform differential expression analysis using DESeq2 Rscript differential_expression.R \${inputDir}/counts.txt \${inputDir}/../results/differential_expression_results.txt \`\`\` Note: The contents of the \`data/\` and \`results/\` directories are not provided as they would depend on the specific input data and expected output structure. `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions