Rewrite symbolic link targets whose paths start with a specified prefix #Shell #file-system

relink_prefix.sh

# This function scans a directory for symbolic links and replaces the
# leading path prefix of each link target with a new prefix while keeping
# the remainder of the path unchanged.
#
# Only links whose targets match the directory boundary pattern
#     OLD_PREFIX/*
# are modified. This prevents accidental matches such as
#     /path/foo2
# when replacing
#     /path/foo
#
# Trailing slashes in prefixes are automatically normalized.
#
# Parameters
# ----------
# BASE_DIR
#     Directory containing symlinks to examine.
#
# OLD_PREFIX
#     Existing path prefix in the symlink targets.
#
# NEW_PREFIX
#     Replacement prefix for the targets.
#
# DRY_RUN (optional)
#     1 → preview changes only (default)
#     0 → apply modifications
#
# Example
# -------
# Mn10Si2Bi1_615 -> /scratch/04996/tg842951/MnBiX_PBE2/Mn10Si2Bi1_615
#
# Running:
#
#     relink_prefix . \
#         /scratch/04996/tg842951/MnBiX_PBE2 \
#         /work2/04996/tg842951/stampede3/run/MnBiX_PBE2
#
# will produce:
#
# Mn10Si2Bi1_615 -> /work2/04996/tg842951/stampede3/run/MnBiX_PBE2/Mn10Si2Bi1_615
#
# Notes
# -----
# - Only symbolic links are processed.
# - Targets not matching OLD_PREFIX are skipped.
# - Absolute paths are recommended.
#
relink_prefix() {
    local base_dir="${1:-.}"
    local old_prefix="${2%/}"
    local new_prefix="${3%/}"
    local dry_run="${4:-1}"

    if [ $# -lt 3 ]; then
        echo "Usage: relink_prefix BASE_DIR OLD_PREFIX NEW_PREFIX [DRY_RUN]"
        return 1
    fi

    find "$base_dir" -type l | while IFS= read -r link; do
        local target suffix new_target
        target=$(readlink "$link") || continue

        case "$target" in
            "$old_prefix"/*)
                suffix="${target#"$old_prefix"}"
                new_target="${new_prefix}${suffix}"

                echo "$link"
                echo "  OLD: $target"
                echo "  NEW: $new_target"

                if [ "$dry_run" != "1" ]; then
                    ln -sfn "$new_target" "$link"
                fi
                ;;
        esac
    done
}