The dynamic linker (ld.so) understands a special token $ORIGIN (or equivalently ${ORIGIN}) in rpath specifications. At runtime, the dynamic linker expands $ORIGIN to the directory containing the executable (or the containing directory of the shared library, if $ORIGIN appears in a shared library’s rpath).

When prog is in bin/ and libraries are in lib/ (sibling directories), the rpath should be:

# $ORIGIN/../lib means: directory of binary / up one level / lib
# This works whether installed at /home/alice/myapp or /opt/tools/myapp

gcc -o bin/prog main.c \
    -Wl,-rpath,'$ORIGIN/../lib' \
    -L./lib -lfoo -lbar

#!/bin/bash
# origin_demo.sh — builds a fully portable self-contained application

set -e
BASE=/tmp/origin_demo

# Create the portable app directory structure
mkdir -p $BASE/bin $BASE/lib

# ---- Library source ----
cat > $BASE/myengine.c << 'EOF'
#include <stdio.h>

void engine_init(void) {
    printf("[libengine] Initializing engine...\n");
}

void engine_run(const char *task) {
    printf("[libengine] Running task: %s\n", task);
}
EOF

# ---- Main program source ----
cat > $BASE/main.c << 'EOF'
#include <stdio.h>

extern void engine_init(void);
extern void engine_run(const char *task);

int main(int argc, char *argv[]) {
    printf("[myapp] Starting at: %s\n", argv[0]);
    engine_init();
    engine_run("data_processing");
    engine_run("report_generation");
    printf("[myapp] Complete!\n");
    return 0;
}
EOF

echo "=== Step 1: Build the shared library ==="
cd $BASE
gcc -g -c -fPIC -Wall myengine.c
gcc -g -shared -Wl,-soname,libengine.so.1 \
    -o lib/libengine.so.1.0.0 myengine.o
ln -sf libengine.so.1.0.0 lib/libengine.so.1
ln -sf libengine.so.1 lib/libengine.so

echo ""
echo "=== Step 2: Build the executable with \$ORIGIN rpath ==="
# IMPORTANT: Single quotes prevent shell from expanding $ORIGIN
gcc -g -Wall \
    -Wl,-rpath,'$ORIGIN/../lib' \
    -o bin/myapp main.c \
    -L./lib -lengine

echo ""
echo "=== Step 3: Verify rpath ==="
objdump -p bin/myapp | grep RPATH
# Should show: RPATH  $ORIGIN/../lib
# (the literal string, NOT expanded yet)

echo ""
echo "=== Step 4: Show ldd with $ORIGIN expanded at runtime ==="
ldd bin/myapp
# Shows: libengine.so.1 => /tmp/origin_demo/lib/libengine.so.1

echo ""
echo "=== Step 5: Run from installation location ==="
./bin/myapp

echo ""
echo "=== Step 6: Simulate installing to a different directory ==="
INSTALL_DIR=/tmp/myapp_install_$(date +%s)
cp -r $BASE $INSTALL_DIR
echo "Installed to: $INSTALL_DIR"
echo "Running from new location:"
$INSTALL_DIR/bin/myapp   # works without any LD_LIBRARY_PATH!

echo ""
echo "=== Done! Works from any install directory ==="

$ORIGIN can also appear in a shared library’s rpath. In that case, $ORIGIN expands to the directory containing the shared library, not the main executable.

#!/bin/bash
# origin_in_lib.sh — $ORIGIN in a shared library's rpath
# Structure:
#   myapp/
#     bin/prog
#     lib/
#       libmain.so      (rpath = $ORIGIN/extra)
#       extra/
#         libextra.so

BASE=/tmp/origin_lib_demo
mkdir -p $BASE/bin $BASE/lib/extra

# ---- libextra.so source (leaf) ----
cat > $BASE/extra_utils.c << 'EOF'
#include <stdio.h>
void extra_func(void) {
    printf("[libextra] extra_func called\n");
}
EOF

# ---- libmain.so source (calls libextra) ----
cat > $BASE/main_lib.c << 'EOF'
#include <stdio.h>
extern void extra_func(void);
void main_func(void) {
    printf("[libmain] main_func calling extra...\n");
    extra_func();
}
EOF

# ---- prog source ----
cat > $BASE/prog.c << 'EOF'
#include <stdio.h>
extern void main_func(void);
int main(void) {
    main_func();
    return 0;
}
EOF

echo "=== Build libextra.so ==="
gcc -shared -fPIC -o $BASE/lib/extra/libextra.so $BASE/extra_utils.c

echo "=== Build libmain.so with \$ORIGIN/extra rpath ==="
gcc -g -c -fPIC $BASE/main_lib.c -o $BASE/main_lib.o
gcc -g -shared \
    -Wl,-rpath,'$ORIGIN/extra' \
    -o $BASE/lib/libmain.so $BASE/main_lib.o \
    -L$BASE/lib/extra -lextra
# $ORIGIN here = /tmp/origin_lib_demo/lib (lib dir of libmain.so)
# So rpath expands to /tmp/origin_lib_demo/lib/extra at runtime

echo ""
echo "rpath in libmain.so:"
objdump -p $BASE/lib/libmain.so | grep RPATH

echo ""
echo "=== Build prog ==="
gcc -g -Wall \
    -Wl,-rpath,'$ORIGIN/../lib' \
    -o $BASE/bin/prog $BASE/prog.c \
    -L$BASE/lib -lmain

echo ""
echo "rpath in prog:"
objdump -p $BASE/bin/prog | grep RPATH

echo ""
echo "=== ldd: complete dependency chain ==="
ldd $BASE/bin/prog

echo ""
echo "=== Run ==="
$BASE/bin/prog

/*
 * Common $ORIGIN rpath patterns for different directory structures
 *
 * Pattern 1: Binary and libs in the same directory
 * ------------------------------------------------
 * app/
 *   prog          <-- rpath: $ORIGIN
 *   libfoo.so.1
 */
// gcc -o app/prog main.c -Wl,-rpath,'$ORIGIN' -L./app -lfoo

/*
 * Pattern 2: Binary in bin/, libs in lib/ (sibling dirs)
 * -------------------------------------------------------
 * app/
 *   bin/
 *     prog        <-- rpath: $ORIGIN/../lib
 *   lib/
 *     libfoo.so.1
 */
// gcc -o bin/prog main.c -Wl,-rpath,'$ORIGIN/../lib' -L./lib -lfoo

/*
 * Pattern 3: Multiple lib directories
 * ------------------------------------
 * app/
 *   bin/
 *     prog        <-- rpath: $ORIGIN/../lib:$ORIGIN/../lib64
 *   lib/
 *     libfoo.so
 *   lib64/
 *     libbar.so
 */
// gcc -o bin/prog main.c \
//     -Wl,-rpath,'$ORIGIN/../lib:$ORIGIN/../lib64' \
//     -L./lib -L./lib64 -lfoo -lbar

/*
 * Pattern 4: Using ${ORIGIN} syntax (useful in Makefiles)
 * ---------------------------------------------------------
 */
// RPATH_FLAG = -Wl,-rpath,'$${ORIGIN}/../lib'  (in Makefile)
// Or use \$\${ORIGIN} depending on Makefile quoting rules

/*
 * Pattern 5: Combining $ORIGIN with absolute path
 * -------------------------------------------------
 * Try private lib first, fall back to system lib
 */
// gcc -o bin/prog main.c \
//     -Wl,-rpath,'$ORIGIN/../lib:/usr/local/lib' \
//     -L./lib -lfoo

/*
 * Verification: read the literal rpath from binary
 */
// objdump -p bin/prog | grep RPATH
// Expected: RPATH  $ORIGIN/../lib
// (NOT expanded — the $ is literal in the ELF file)