restic -r /Volumes/BackupManual/restic-backups snapshots

ID        Date                 Host        Tags            Directory
----------------------------------------------------------------------
dbc3943d  2017-02-07 18:50:47  User.fritz.box                  /Users/user/Documents
bd355ca9  2017-02-07 19:57:59  User.fritz.box                  /Users/user/Documents

restic -r /Volumes/BackupManual/restic-backups forget IDxxxxxx

#!/bin/bash

# USER CONFIGURATION:
resticuser=restic
srcdir=/Users/user/data
backupvolume=/Volumes/usb-storage-name
backupdir=${backupvolume}/restic-backups

# Script vars:
longname=$0
shortname=$(/usr/bin/basename "${longname}")

printf '%s %s (%s) running...n' "$(date -u "+%Y-%m-%d %H:%M:%S")" "${shortname}" "${longname}"

if [[ ! -d "${srcdir}" ]]; then
    printf '%s %s does NOT exist.' "$(date -u "+%Y-%m-%d %H:%M:%S")" "${srcdir}" >&2
    exit 1
else
    if [[ $(mount | grep "${backupvolume}") ]]; then
        # See: http://blog.macromates.com/2006/keychain-access-from-shell/
        # Parse output of 'security' and set RESTIC_PASSWORD:
        export RESTIC_PASSWORD=$(security 2>&1 >/dev/null find-generic-password -ga ${resticuser} |ruby -e 'print $1 if STDIN.gets =~ /^password: "(.*)"$/')
        # Run backup, capturing output in case of error:
        output=$(restic -r ${backupdir} backup "${srcdir}")
        error=$?
        if [[ "${error}" == "0" ]]; then
            printf '%s Restic backup completed successfully.n' "$(date -u "+%Y-%m-%d %H:%M:%S")"
        else
            printf '%s Restic backup failed: error code: %s, error: %sn'
                    "$(date -u "+%Y-%m-%d %H:%M:%S")" "${error}" "${output}" >&2
        fi
    else
        printf '%s %s is NOT mounted.' "$(date -u "+%Y-%m-%d %H:%M:%S")" "${backupvolume}" >&2
        exit 1
    fi
fi

printf '%s %s ended.n' "$(date -u "+%Y-%m-%d %H:%M:%S")" "${shortname}"