6 files changed, 121 insertions, 0 deletions
diff --git a/tools/each b/tools/each
new file mode 100755
index 0000000..da5ce84
--- /dev/null
+++ b/tools/each
@@ -0,0 +1,21 @@
+#!/bin/sh
+
+if [ -z "$1" ]; then
+    echo "Usage: $0 <command>"
+    echo ""
+    echo "Run the given command for each newline-separated line in stdin (think for-each in many programming languages)."
+    echo 'The iterator variable is called "$ELEM", and the index variable is called "$IDX".'
+    exit 1
+fi
+
+i=0
+while IFS=$'\n' read -r line; do
+    j=0
+    for item in $line; do
+        eval "X${j}='$item'"
+        j=$((j+1))
+    done
+
+    IDX=$i ELEM="$line" eval "$1"
+    i=$((i+1))
+done
diff --git a/tools/filter b/tools/filter
new file mode 100755
index 0000000..94258d0
--- /dev/null
+++ b/tools/filter
@@ -0,0 +1,25 @@
+#!/bin/sh
+
+if [ -z "$1" ]; then
+    echo "Usage: $0 <command>"
+    echo ""
+    echo "Run the given test expression for each newline-separated line in stdin, and echo only the lines that return zero."
+    echo "(Think filter in many programming languages)."
+    echo 'The iterator variable is called "$ELEM", and the index variable is called "$IDX".'
+    exit 1
+fi
+
+i=0
+while IFS=$'\n' read -r line; do
+    j=0
+    for item in $line; do
+        eval "X${j}='$item'"
+        j=$((j+1))
+    done
+
+    IDX=$i ELEM="$line" eval "test $1"
+    if [ $? -eq 0 ]; then
+        echo "$line"
+    fi
+    i=$((i+1))
+done
diff --git a/tools/map b/tools/map
new file mode 100755
index 0000000..8c4e5ef
--- /dev/null
+++ b/tools/map
@@ -0,0 +1,21 @@
+#!/bin/sh
+
+if [ -z "$1" ]; then
+    echo "Usage: $0 <expr>"
+    echo ""
+    echo "Give the given expression for each newline-separated line in stdin as an argument to echo (think map in many programming languages)."
+    echo 'The iterator variable is called "$ELEM", and the index variable is called "$IDX".'
+    exit 1
+fi
+
+i=0
+while IFS=$'\n' read -r line; do
+    j=0
+    for item in $line; do
+        eval "X${j}='$item'"
+        j=$((j+1))
+    done
+
+    IDX=$i ELEM="$line" eval "echo $1"
+    i=$((i+1))
+done
diff --git a/tools/reduce b/tools/reduce
new file mode 100755
index 0000000..effb98d
--- /dev/null
+++ b/tools/reduce
@@ -0,0 +1,27 @@
+#!/bin/sh
+
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 <init> <expr>"
+    echo ""
+    echo "Run the given command for each newline-separated line in stdin."
+    echo 'The expression computes the next value of "$ACC" (think reduce in many programming languages).'
+    echo 'The initial value of "$ACC" is the first argument to the script.'
+    echo 'The iterator variable is called "$ELEM", and the index variable is called "$IDX".'
+    echo 'The final value of "$ACC" is printed after all lines have been processed.'
+    exit 1
+fi
+
+i=0
+ACC="$1"
+while IFS=$'\n' read -r line; do
+    j=0
+    for item in $line; do
+        eval "X${j}='$item'"
+        j=$((j+1))
+    done
+
+    IDX=$i ELEM="$line" eval "ACC=\"$2\""
+    i=$((i+1))
+done
+
+echo "$ACC"
diff --git a/tools/splitat b/tools/splitat
new file mode 100755
index 0000000..d41521e
--- /dev/null
+++ b/tools/splitat
@@ -0,0 +1,14 @@
+#!/bin/sh
+
+if [ "$#" -ne 1 ]; then
+    echo "Usage: $0 <separator>"
+    echo ""
+    echo "Split the stdin into lines, splitting at the given separator character."
+    exit 1
+fi
+
+while IFS=$'\n' read -r line; do
+    for part in $(echo "$line" | tr "$1" '\n'); do
+        echo "$part"
+    done
+done
diff --git a/tools/words b/tools/words
new file mode 100755
index 0000000..ac76d0d
--- /dev/null
+++ b/tools/words
@@ -0,0 +1,13 @@
+#!/bin/sh
+
+if [ "$#" -ne 0 ]; then
+    echo "Usage: $0"
+    echo ""
+    echo "Echo each whitespace-separated word in stdin on a new line."
+    exit 1
+fi
+
+i=0
+for word in $(cat); do
+    echo "$word"
+done