initial commit

bash/grep/grep.sh

@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+
+usage () {
+    echo "usage: grep.sh [-nlivx] [-e] pattern file [...]"
+    exit 1
+}
+
+# no arguments
+LN=                                               # be sure variables are reset
+FN=
+RV=
+FL=
+MULTI=
+
+# parse args:
+while getopts ":nlivxe" arg; do
+    case $arg in
+        n) LN=t ;;                                # will print line number
+        l) FN=t ;;                                # only file names
+        i) shopt -s nocasematch ;;                # case insensitive
+        v) RV=t ;;                                # reverse search
+        x) FL=t ;;                                # full line search
+        e) break ;;                               # not in exercise: end args
+        *) usage ;;
+    esac
+done
+shift $((OPTIND-1))
+
+# need at least pattern and 1 file.
+# TODO: consider stdin if no file
+[[ $# < 2 ]] && usage
+[[ $# > 2 ]] && MULTI=t
+
+# full line match
+if [[ $FL = t ]]; then
+    pattern="^$1\$"
+else
+    pattern=".*$1.*"
+fi
+
+shift
+
+# will prevent leading/trailing whitespaces to be trimmed
+IFS=""
+
+while [[ $# > 0 ]]; do
+    file="$1"
+    if [[ ! -r "$file" ]]; then
+        echo "$file: no such file, or not readable."
+        exit 1
+    fi
+
+    lnum=0                                        # line number
+
+    match=n
+    while read -r line ; do                        # will consider '\' as normal char
+        (( lnum ++ ))
+
+        if [[ $line =~ $pattern ]] ; then         # line match
+            match=y
+
+            # print only filename, go to next file
+            [[ $FN = t ]] && echo "$file" && break
+
+            # not reverse matching only
+            if [[ $RV != t ]]; then
+                # multiple files: print filename
+                [[ $MULTI == t ]] && echo -n "$file:"
+                [[ $LN = t ]] && echo -n "$lnum:"
+                echo "$line"
+            fi
+        else
+            # reverse match
+            if [[ $RV == t ]]; then
+                # print only filename, go to next file
+                [[ $FN = t ]] && echo "$file" && break
+
+                # multiple files: print filename
+                [[ $MULTI == t ]] && echo -n "$file:"
+                [[ $LN = t ]] && echo -n "$lnum:"
+                echo "$line"
+            fi
+        fi
+    done < "$1"
+
+    shift                                         # next file
+done
+exit 0